Add wrappers for dlopen, dlsym, and glXGetProcAddressARB

This allows for many applications to start working with fips that would not
work before. Specifically, applications that dlopen libGL.so.1 instead of
directly linking with it would previously bypass fips' attempts to wrap
GL calls.

With these new wrappers carefully in place, many applications now work.

I've verified the following applications at least:

	apitrace replay
	NightSkyHD, a Humble Bundle game, both 32 and 64-bit versions
	World of Goo, via Steam

I was also happy to notice that the Steam overlay does not cause fips
any difficulties.