Introduce the Termination Port API

* Moved the error codes to jerry-port.h and declared port function
  `jerry_port_fatal`.

* Moved "exit or abort on fail" functionality to the newly added
  jerry-port-default-fatal.c.

* This implied that a default port-specific API had to be introduced:
  functions `jerry_port_default_set_abort_on_fail` and
  `jerry_port_default_is_abort_on_fail` declared in jerry-port-default.h
  control the fatal exit behaviour.

* For the sake of clarity, renamed jerry-port.c to
  jerry-port-default-io.c.

* Adapted CMakeLists to deal with port implementations consisting of
  more then one source file and exposing headers. This also required
  the renaming of `EXTERNAL_PORT_FILE` cmake option to
  `EXTERNAL_PORT_DIR`.

* Adapted main sources to use the default port header for the
  abort-on-fail functionality, as that is not part of the core jerry
  API anymore.

* Added default port implementation to the static source code checker
  tools.

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

main-unix.c

@@ -20,6 +20,7 @@
 
 #include "jerry.h"
 #include "jerry-port.h"
+#include "jerry-port-default.h"
 
 /**
  * Maximum command line arguments number
@@ -358,7 +359,7 @@ main (int argc,
     }
     else if (!strcmp ("--abort-on-fail", argv[i]))
     {
-      flags |= JERRY_FLAG_ABORT_ON_FAIL;
+      jerry_port_default_set_abort_on_fail (true);
     }
     else if (!strncmp ("-", argv[i], 1))
     {