Use preallocated permanent zvals instead of null, true, false, 0 and 1

[ghost]

This is what was implemented in 2.0.0 / Zephir and appears to be very useful optimization. In some cases it helps avoid creation of the memory frame because we don't need PHALCON_INIT_VAR anymore.

In addition, this PR fixes the bug when a function calls another function (passing it its return_value and return_value_ptr) and the called function throws an exception:

PHP_FUNCTION(test1)
{
    phalcon_call_function_p0_ex(return_value, return_value_ptr, "test2");
}

PHP_FUNCTION(test2)
{
    zend_throw_exception(...);
}

In this scenario, Zend (zend_call_function()) detects the exception and frees the variable return_value_ptr points to. But because test1 passed to test2 its own return_value/return_value_ptr, test2 frees test1's return value. Then, after test2 and test1 return, Zend sees there is an active exception and tries to free the return value of test1 which was already freed on return from test2 and segmentation fault happens.

We tried to address this issue in the past (in phalcon_alt_call_method) but that fix is not applicable to all kinds of static calls because they are dispatched via zend_call_function.

[phalcon]

Great!