[API] Introduce jerry_parse_and_save_literals()

This function can be used to save literals into a specific file in a list or C format.
These literals are valid identifiers, and doesn't match to any magic-string.
The '--save-literals-list-format FILE' and '--save-literals-c-format FILE'
options are used to save into the given file, when the snapshot-save is enabled.
The saved literals are sorted by size and lexicographically.
The C-format is useful for jerry_register_magic_strings() to generate the array
of external magic strings.

JerryScript-DCO-1.0-Signed-off-by: Zsolt Borbély zsborbely.u-szeged@partner.samsung.com

Author: Zsolt Borbély

docs/02.API-REFERENCE.md

@@ -296,6 +296,7 @@ jerry_register_magic_strings  (const jerry_char_ptr_t *ex_str_items_p,
 
 - [jerry_init](#jerry_init)
 - [jerry_cleanup](#jerry_cleanup)
+- [jerry_parse_and_save_literals](#jerry_parse_and_save_literals)
 
 
 ## jerry_get_memory_limits
@@ -3204,3 +3205,59 @@ jerry_exec_snapshot (const void *snapshot_p,
 - [jerry_init](#jerry_init)
 - [jerry_cleanup](#jerry_cleanup)
 - [jerry_parse_and_save_snapshot](#jerry_parse_and_save_snapshot)
+
+
+## jerry_parse_and_save_literals
+
+**Summary**
+
+Collect and save the used literals from the specified source code.
+
+**Prototype**
+
+```c
+size_t
+jerry_parse_and_save_literals (const jerry_char_t *source_p,
+                               size_t source_size,
+                               bool is_strict,
+                               uint8_t *buffer_p,
+                               size_t buffer_size,
+                               bool is_c_format);
+```
+
+- `source_p` - script source, it must be a valid utf8 string.
+- `source_size` - script source size, in bytes.
+- `is_strict` - strict mode
+- `buffer_p` - buffer to save literals to.
+- `buffer_size` - the buffer's size.
+- `is_c_format` - the output format would be C-style (true) or a simple list (false).
+- return value
+  - the size of the literal-list, if it was generated succesfully (i.e. the list of literals isn't empty,
+    and literal-save support is enabled in current configuration through JERRY_ENABLE_SNAPSHOT_SAVE)
+  - 0 otherwise.
+
+**Example**
+
+```c
+{
+  jerry_init (JERRY_INIT_EMPTY);
+
+  static uint8_t save_literal_buffer[1024];
+  const jerry_char_t *code_for_literal_save_p = "var obj = { a:'aa', bb:'Bb' }";
+
+  size_t literal_sizes = jerry_parse_and_save_literals (code_for_literal_save_p,
+                                                        strlen ((const char *) code_for_literal_save_p),
+                                                        false,
+                                                        save_literal_buffer,
+                                                        sizeof (save_literal_buffer),
+                                                        true);
+
+  jerry_cleanup ();
+}
+```
+
+**See also**
+
+- [jerry_init](#jerry_init)
+- [jerry_cleanup](#jerry_cleanup)
+- [jerry_register_magic_strings](#jerry_register_magic_strings)

jerry-core/jerry-api.h

@@ -320,6 +320,8 @@ bool jerry_foreach_object_property (const jerry_value_t obj_val, jerry_object_pr
 size_t jerry_parse_and_save_snapshot (const jerry_char_t *source_p, size_t source_size, bool is_for_global,
                                       bool is_strict, uint8_t *buffer_p, size_t buffer_size);
 jerry_value_t jerry_exec_snapshot (const void *snapshot_p, size_t snapshot_size, bool copy_bytecode);
+size_t jerry_parse_and_save_literals (const jerry_char_t *source_p, size_t source_size, bool is_strict,
+                                      uint8_t *buffer_p, size_t buffer_size, bool is_c_format);
 
 /**
  * @}