Update doxygen and fix documentation (#5106)

Update Doxyfile to version 1.9.1

Re-enable doxygen CI checker

Fix some regular comments that should have been doc comments

Document void return types for some inline functions explicitly

Move start of some doxygen groups so they are included always, and not left
out of certain ifdefs

Ignore some doxygen warnings:
    Member (function) is not documented in headers
    Documented empty return type in headers
    Argument has multiple @param documentation sections

JerryScript-DCO-1.0-Signed-off-by: Máté Tokodi mate.tokodi@szteszoftver.hu

jerry-core/include/jerryscript-port.h

@@ -55,9 +55,8 @@ typedef enum
  *
  * A libc-based port may implement this with exit() or abort(), or both.
  *
- * Note: This function is expected to not return.
- *
  * @param code: the cause of the error.
+ * @return This function is expected to not return.
  */
 void JERRY_ATTR_NORETURN jerry_port_fatal (jerry_fatal_code_t code);
 
@@ -115,8 +114,6 @@ struct jerry_context_t *jerry_port_context_get (void);
  *
  * This port function is called by jerry_cleanup when JERRY_EXTERNAL_CONTEXT is enabled.
  * Otherwise this function is not used.
- *
- * @return the pointer to the engine context.
  */
 void jerry_port_context_free (void);