Move jerry-core API implementations and headers into dedicated subdirectories (#1793)

Moved all public API headers under the `jerry-core/include`
directory. This makes installing all the public headers easier.
Also, should we have new public headers in the future, their
installation will be automatic, there will be no need to update the
build files. Moreover, this aligns better with the structure of
other libraries in the project (in those cases, public headers
always reside in `<library>/include`).

Moved all public API implementations under the `jerry-core/api`
directory. This cleans up the root directory of `jerry-core`,
moving all implementation code under "modules", i.e.,
subdirectories. This also makes the future splitting of the big and
monolithic `jerry.c` along features easier, if needed. (Debugger
and snapshot-related functions are already in separate sources.)

Notes:
* `jerryscript.h` is split up to separate header files along
  feature boundaries. These new headers are included by
  `jerryscript.h`, so this is not a breaking change but header
  modularization only.
* `jerry-snapshot.h` is still under `jerry-core/api`, keeping it as
  a non-public header.
* This commit also adapts all targets to the include path change.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-core/include/jerryscript-port.h

@@ -0,0 +1,161 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef JERRYSCRIPT_PORT_H
+#define JERRYSCRIPT_PORT_H
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif /* __cplusplus */
+
+/** \addtogroup jerry_port Jerry engine port
+ * @{
+ */
+
+/*
+ * Termination Port API
+ *
+ * Note:
+ *      It is questionable whether a library should be able to terminate an
+ *      application. However, as of now, we only have the concept of completion
+ *      code around jerry_parse and jerry_run. Most of the other API functions
+ *      have no way of signaling an error. So, we keep the termination approach
+ *      with this port function.
+ */
+
+/**
+ * Error codes
+ */
+typedef enum
+{
+  ERR_OUT_OF_MEMORY = 10,
+  ERR_SYSCALL = 11,
+  ERR_REF_COUNT_LIMIT = 12,
+  ERR_FAILED_INTERNAL_ASSERTION = 120
+} jerry_fatal_code_t;
+
+/**
+ * Signal the port that jerry experienced a fatal failure from which it cannot
+ * recover.
+ *
+ * @param code gives the cause of the error.
+ *
+ * Note:
+ *      Jerry expects the function not to return.
+ *
+ * Example: a libc-based port may implement this with exit() or abort(), or both.
+ */
+void jerry_port_fatal (jerry_fatal_code_t code);
+
+/*
+ *  I/O Port API
+ */
+
+/**
+ * Jerry log levels. The levels are in severity order
+ * where the most serious levels come first.
+ */
+typedef enum
+{
+  JERRY_LOG_LEVEL_ERROR,    /**< the engine will terminate after the message is printed */
+  JERRY_LOG_LEVEL_WARNING,  /**< a request is aborted, but the engine continues its operation */
+  JERRY_LOG_LEVEL_DEBUG,    /**< debug messages from the engine, low volume */
+  JERRY_LOG_LEVEL_TRACE     /**< detailed info about engine internals, potentially high volume */
+} jerry_log_level_t;
+
+/**
+ * Display or log a debug/error message. The function should implement a printf-like
+ * interface, where the first argument specifies the log level
+ * and the second argument specifies a format string on how to stringify the rest
+ * of the parameter list.
+ *
+ * This function is only called with messages coming from the jerry engine as
+ * the result of some abnormal operation or describing its internal operations
+ * (e.g., data structure dumps or tracing info).
+ *
+ * It should be the port that decides whether error and debug messages are logged to
+ * the console, or saved to a database or to a file.
+ *
+ * Example: a libc-based port may implement this with vfprintf(stderr) or
+ * vfprintf(logfile), or both, depending on log level.
+ */
+void jerry_port_log (jerry_log_level_t level, const char *format, ...) __attribute__ ((format (printf, 2, 3)));
+
+/*
+ * Date Port API
+ */
+
+/**
+ * Jerry time zone structure
+ */
+typedef struct
+{
+  int offset;                /**< minutes from west */
+  int daylight_saving_time;  /**< daylight saving time (1 - DST applies, 0 - not on DST) */
+} jerry_time_zone_t;
+
+/**
+ * Get timezone and daylight saving data
+ *
+ * @return true  - if success
+ *         false - otherwise
+ */
+bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p);
+
+/**
+ * Get system time
+ *
+ * @return milliseconds since Unix epoch
+ */
+double jerry_port_get_current_time (void);
+
+/*
+ * JobQueue Port API
+ */
+
+/**
+ * Jerry job handler function type
+ */
+typedef uint32_t (*jerry_job_handler_t) (void *);
+
+/**
+ * Enqueue a job described by a pair of function and data pointers. The port is
+ * expected to call the handler function with the given data at some (later)
+ * point of time.
+ *
+ * @param handler the pointer of the handler function associated with the job.
+ * @param job_p the data pointer to be passed to handler when called.
+ *
+ * Note:
+ *      This port function is only called by the implementation of the Promise
+ *      builtin (mandated by the ES2015 standard). If the engine is built with
+ *      Promise disabled (e.g., with ES5.1 profile), then the port does not have
+ *      to implement this function.
+ */
+void jerry_port_jobqueue_enqueue (jerry_job_handler_t handler, void *job_p);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+#endif /* !JERRYSCRIPT_PORT_H */