Bugfix/use correct symbol table php71

[mathieuk]

I tried using php-meminfo to investigate a problem with classes not being released somewhere but ran into a few snags when running with PHP 7.1 / PHP 7.2 which I hope to address in this PR. I've verified this to work (more accurately) in PHP 7.1 and expect it to run in PHP 7.2.

• When I assigned a variable to a property on 'the current object' (as in, the object whose method I ran meminfo_dump() in) that property would get ignored as it was a seen as a reference. This change dereferences any references.
• I ended up with the same data over and over again and I wouldn't find variables I'd expect to find in the output of php-meminfo. It appears PHP 7.1+ has changed the way symbol tables are referenced. This change reflects that.

[BitOne]

Thanks @mathieuk , it indeed fixes the frame browsing problem with PHP 7.1