Count the number of parameters a function call has been passed.

Expects to be passed the T_STRING stack pointer for the function call.
If passed a T_STRING which is *not* a function call, the behaviour is unreliable.

Extra feature: If passed an T_ARRAY or T_OPEN_SHORT_ARRAY stack pointer,
it will return the number of values in the array.

@link https://github.com/PHPCompatibility/PHPCompatibility/issues/111
@link https://github.com/PHPCompatibility/PHPCompatibility/issues/114
@link https://github.com/PHPCompatibility/PHPCompatibility/issues/151

@since 0.11.0

@param int $stackPtr The position of the function call token.

@return int