remove unused tx64 methods

remove dead tx64 code

due to sandcastle flakiness per bsimmers:
Remove the ImageSprite extension

Believed to be unused now.
Move TestExtMath to php
TestExtOptions, TestExtNetwork, TestExtSocket -> php
Match Zend behavior on openssl_pkey_get_details

Zend PHP populates an extra field in the details array
with some more information about the resource it is passed,
while HHVM leaves this information out.

Closes #815
make o_toBoolean non-virtual

I know this is bad form, but we need this for performance. Right now, o_toBoolean() isn't even being called. When D825610 lands it will be and will be a small perf regression.

If this situation gets bad, then we should revisit it, but since only one class is overriding it for now, this should be ok.

(I don't understand C++, did I do the virtual thing right? I had to declare them to make the linker work)
actually implement SplObjectStorage
Fix crashes with empty string as SetElem base

It needs to convert the key to a real TypedValue, and needs
to side exit (via throw).
add filter extension
Split lvalPtr() into createLvalPtr/getLvalPtr()

Callers are always passing a constant to choose one or the other,
so make them distinct methods.
Fix tvSame for null-by-reference values

The dereference was too late.