GLdispatch: Export __glDispatchSetCurrentThreadState

This seems to be the shortest path to getting Delay working. It's kind
of playing with fire, hence the warning, but it does seem to work if
you're careful.

Another option that I considered was to use dlmopen() to put libEGL into
its own link map (and thus own TLS scope). That doesn't work because of
dlmopen bugs, and wouldn't be portable outside of glibc and Solaris.

Another another option I consider was to add a new GLDISPATCH_API_BLAH
enum and teach the frontend libraries to handle it. This got ugly
quickly, in part because I think that ends up wanting additional API
between the frontend and vendor library without having a good way to
signal from the frontend that that API is available. So if we're adding
API anyway, simply exporting one function we already have seems quite a
bit simpler.
2 jobs for delay in 1 minute and 47 seconds (queued for 1 second)