Fix FFI Parsing of Pointer Declaration Lists

[davnotdev]

struct MyStruct {
    uint8_t** a, *b, c;
};

When a struct is defined in this form, the "base type" of a, b, and c is uint8_t**, so a will be uint8_t**, b will be uint8_t***, and c will be uint8_t**. This PR fixes the issue and adds a test case for it.

[bwoebi]

This file is generated from ext/ffi/ffi.g, so you should fix that one too.

But thanks for fixing and the test!

[dstogov]

@davnotdev thanks for catching and fixing this.
@bwoebi thank you for the grammar correction.

[dstogov]

The test case might be simplified, but the existing one is also good enough.

$ffi = FFI::cdef(<<<EOF
    struct MyStruct {
        uint8_t** a, *b, c;
    };
EOF);
$x = $ffi->new("struct MyStruct");
var_dump(FFI::typeof($x->a));
var_dump(FFI::typeof($x->b));
var_dump(FFI::typeof($x->c));