FFI:Add support multiple instance struct pointer compatible and callback error contain args offset

[chopins]

change:
1. zend_ffi_is_compatible_type()
support check same name struct pointer of multiple FFI instance

Pseudo code：

<?php
$ffi1 = FFI::cdef("
typedef struct _a {
int a;
}
");
$ffi2 = FFI::cdef("
typedef struct _a {
int a;
}
extern void test (a* instance);
"
);
$av = $ffi1->new('a*');
$ffi2->test($av); //exec success, do not trigger segfaults or type incompatible error
?>

2. zend_ffi_create_callback()
report error message that contain offset of parameter
when has argc, will report below message:
Variadic function closures are not supported, parameter 1 occur
Attempt to assign parameter 1 to be invalid callback, %s
Attempt to assign parameter 1 to be invalid callback, insufficient number of arguments
Cannot allocate callback, parameter 1 occur

[dstogov]

hi @chopins,

1. The first part of the patch (zend_ffi_is_compatible_type()) is incorrect. If you mix two different FFI objects with different C declarations, they may declare different structures with the same name. In general, you shouldn't mix different FFI objects or perform C casts.

2. variadic callbacks. I've tested the patch, and it seems doesn't work as expected:

<?php
$ffi = FFI::cdef("
size_t (*zend_printf)(const char *format, ...);
");
$ffi->zend_printf = function ($format, ...$args) {
	var_dump($format, $args);
};
$f = $ffi->zend_printf;
$f("%s:%d:%d\n", "str", 5, 3);
?>

Please, use separate patches//PRs for different features.

[chopins]

@dstogov
for incorrect, I will test again and fix it
for mix object type, this is convenient features, and not conflict different structures with the same name, the developer to decide how to use.
multiple dll load convenience will enhance the usefulness of FFI

[chopins]

i remove variadic callbacks feature

[chopins]

use pure php implement