This does not add any build stuff or new sample code yet, it just does
some prep to our C++ codebase:
- Similar to Android, WebAssembly will not be using BlueGL. We were
using a mixture of #if and #ifdef when checking for the existence of
certain GL prototypes, but the latter is what we want in order to
build robustly with any GL headers. (We still perform run-time checks
for extensions, this doesn't change that.)
- Add a trivial ContextManager, does a bit more than Dummy since it
needs to create an actual driver. This doesn't get compiled yet, it
just adds files to the tree.
- WebAssembly does not support mmap, execinfo, or asm volatile.