[API] Add RegExp C API (#2542)

This patch supports creating a RegExp object through the C API.

JerryScript-DCO-1.0-Signed-off-by: Daniel Balla dballa@inf.u-szeged.hu

docs/02.API-REFERENCE.md

@@ -62,6 +62,16 @@ Possible compile time enabled feature types:
  - JERRY_FEATURE_LINE_INFO - line info available
  - JERRY_FEATURE_LOGGING - logging
 
+## jerry_regexp_flags_t
+
+RegExp object optional flags:
+
+  - JERRY_REGEXP_FLAG_GLOBAL - global match; find all matches rather than stopping after the first match
+  - JERRY_REGEXP_FLAG_IGNORE_CASE - ignore case
+  - JERRY_REGEXP_FLAG_MULTILINE - multiline; treat beginning and end characters (^ and $) as working over
+  multiple lines (i.e., match the beginning or end of each line (delimited by \n or \r), not only the
+  very beginning or end of the whole input string)
+
 ## jerry_parse_opts_t
 
 Option bits for [jerry_parse](#jerry_parse) and
@@ -3406,6 +3416,74 @@ jerry_create_string_sz (const jerry_char_t *str_p,
 - [jerry_create_string_from_utf8](#jerry_create_string_from_utf8)
 
 
+## jerry_create_regexp
+
+**Summary**
+
+Returns a jerry_value_t RegExp object or an error, if the construction of the object fails.
+Optional flags can be set using [jerry_regexp_flags_t](#jerry_regexp_flags_t);
+
+**Prototype**
+```c
+jerry_value_t
+jerry_create_regexp (const jerry_char_t *pattern_p, jerry_regexp_flags_t flags);
+```
+
+- `pattern_p` - the RegExp pattern as a zero-terminated UTF-8 string
+- `flags` - optional flags for the RegExp object
+- return value - the RegExp object as a `jerry_value_t`
+
+**Example**
+
+```c
+{
+  jerry_char_t pattern_p = "[cgt]gggtaaa|tttaccc[acg]";
+  jerry_regexp_flags_t pattern_flags = JERRY_REGEXP_FLAG_IGNORE_CASE;
+
+  jerry_value_t regexp = jerry_create_regexp (pattern_p, pattern_flags);
+
+  ...
+
+  jerry_release_value (regexp);
+}
+```
+
+
+## jerry_create_regexp_sz
+
+**Summary**
+
+Returns a jerry_value_t RegExp object or an error, if the construction of the object fails.
+Optional flags can be set using [jerry_regexp_flags_t](#jerry_regexp_flags_t);
+
+**Prototype**
+```c
+jerry_value_t
+jerry_create_regexp_sz (const jerry_char_t *pattern_p, jerry_size_t pattern_size, jerry_regexp_flags_t flags);
+```
+
+- `pattern_p` - the RegExp pattern as a zero-terminated UTF-8 string
+- `pattern_size` - size of the `pattern`
+- `flags` - optional flags for the RegExp object
+- return value - the RegExp object as a `jerry_value_t`
+
+**Example**
+
+```c
+{
+  jerry_char_t pattern_p = "[cgt]gggtaaa|tttaccc[acg]";
+  jerry_size_t pattern_size = sizeof (pattern_p) - 1;
+  jerry_regexp_flags_t pattern_flags = JERRY_REGEXP_FLAG_IGNORE_CASE;
+
+  jerry_value_t regexp = jerry_create_regexp_sz (pattern_p, pattern_size, pattern_flags);
+
+  ...
+
+  jerry_release_value (regexp);
+}
+```
+
+
 ## jerry_create_typedarray
 
 **Summary**