Add C API to query the type of a JS value (#2195)

New API function:
 * jerry_value_get_type

JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.u-szeged@partner.samsung.com

docs/02.API-REFERENCE.md

@@ -11,6 +11,19 @@ Enum that contains the following elements:
  - JERRY_INIT_MEM_STATS_SEPARATE - dump memory statistics and reset peak values after parse
  - JERRY_INIT_DEBUGGER - deprecated, an unused placeholder now
 
+## jerry_type_t
+
+Enum that contains a set of elements to represent JavaScript type:
+
+ - JERRY_TYPE_NONE - no type information
+ - JERRY_TYPE_UNDEFINED - undefined value
+ - JERRY_TYPE_NULL - null value
+ - JERRY_TYPE_BOOLEAN - boolean value
+ - JERRY_TYPE_NUMBER - number value
+ - JERRY_TYPE_STRING - string value
+ - JERRY_TYPE_OBJECT - object value
+ - JERRY_TYPE_FUNCTION - function value
+
 ## jerry_error_t
 
 Possible types of an error:
@@ -1447,6 +1460,44 @@ jerry_value_is_undefined (const jerry_value_t value)
 
 - [jerry_release_value](#jerry_release_value)
 
+## jerry_value_get_type
+
+**Summary**
+
+Returns the JavaScript type
+for a given value as a [jerry_type_t](#jerry_type_t) enum value.
+
+This is a similar operation as the 'typeof' operator
+in the standard with an exception that the 'null'
+value has its own enum value.
+
+**Prototype**
+
+```c
+jerry_type_t
+jerry_value_get_type (const jerry_value_t value);
+```
+
+**Example**
+
+```c
+{
+  jerry_value_t number = jerry_create_number (3.3);
+
+  jerry_type_t type_info = jerry_value_get_type (number);
+
+  if (type_info == JERRY_TYPE_NUMBER)
+  {
+    ...
+  }
+
+  jerry_value_release (number);
+}
+```
+
+**See also**
+- [jerry_type_t](#jerry_type_t)
+
 ## jerry_is_feature_enabled
 
 **Summary**