Most of the changes that happened after commit 8bbc0d40 broke epoxy
pretty much irreparably because of the CMake build and the attempt at
making libepoxy a static library that can be copy-pasted into another
project without generating files.
Since all the commits are entangled, and are full of unrelated changes,
we cannot simply do a localized set of reverts; instead, we need to hit
the reset button.
From this point forward, we're going to improve libepoxy's build while
attempting to keep the existing build system working. This may mean
reinstating the CMake build system at a later date.
Epoxy dlsym()s directly into libEGL instead of using dlsym() on a NULL
handle, so we can't relying on ELF resolution like we do for dlopen().
Instead, just override epoxy's function pointers for the functions
epoxy will call in the process of getting one of these bootstrap
functions.