In testpatchentrypoints, remove the additional calls to glVertex3fv after
releasing the current context.
libGLdispatch doesn't unpatch entrypoints from __glDispatchLoseCurrent anymore,
so those calls will still increment the __glXSawVertex3fv counter.
This means that it no longer tests entrypoint unpatching, but fixing that would
require multiple vendor libraries, which with GLX requires multiple screens.
Remove the libGLX_patchentry dummy vendor library. The libGLX_dummy.so library
will provide the entrypoint patching callbacks based on an environment
variable.
This unit test verifies that entrypoint patching works as expected, by
loading libGLX_patchentry.so, looking up the address of
__glXSawVertex3fv defined in libGLX_patchentry.so, and verifying that
the value at this symbol matches the number of calls to glVertex3fv()
(which is hacked to increment __glXSawVertex3fv via entrypoint
rewriting).
