Call PHP function.

`phalcon_call_func_p2` macro is defined in ext/kernel/fcall.h

Macros to call function/methods look like this:

  1. phalcon_call_WHAT(return_value, function)
  2. phalcon_call_WHAT_noret(function)
  3. phalcon_call_WHAT_pN(return_value, function, parameters)
  4. phalcon_call_WHAT_pN_noret(function, parameters)

WHAT is `func` (for function), `method` (method), `static` (static function), `parent` (parent function)
N is the number of arguments.

_noret() variants discard the return value.