This is important for testing the TSD stubs, which have a separate fast path
for single-threaded programs.
The TSD stubs start with a simple global variable to hold the dispatch table
so that a single-threaded program doesn't have to deal with the overhead of
calling pthread_getspecific. When a second thread comes along, it sets that
variable to NULL, which makes the stubs call pthread_getspecific instead.
This change adds a flag to the testgldispatch test program that tells it to
call into libGLdispatch from two threads to force it into its multi-threaded
mode.
It also adds three new test scripts, which are the same testgldispatch tests
but for the multithreaded path.
Replaced testpatchentrypoints_gldispatch with three new unit tests.
testgldispatch_static and testgldispatch_generated test dispatching to multiple
vendor libraries through static and generated dispatch stubs, respectively.
testgldispatch_generated tests entrypoint patching and unpatching. This adds
coverage for patching generated stubs in addition to the static ones.
The entrypoint patching functions in tests/dummy/patchentrypoints.c now take
the name of the function to patch, instead of hard-coding it to only patch
glVertex3fv.
