Previously this relied on getting all known classes/functions/etc
when it was loaded, and then again after the PHP module being
tested was loaded. This approach no longer works now we've
stopped loading modules using dl(), so use ReflectionExtension
instead to get information about a specific extension.
This is likely also faster than wading through lists including
everything predefined by PHP.
Stop filtering /^new_/ - we no longer generate these for classes, so
only the li_carrays and li_carrays_cpp testcases generate new_* flat
functions, and it's helpful to check those are generated.
Stop filtering /_(alter|get)_newobject$/' - we no longer generate
these, as they weren't used or documented.
