package/libepoxy: bump to version 1.5.9

Update to libepoxy 1.5.9, which adds a fallback to use libOpenGL.so that
fixes a couple of regressions:

  https://github.com/anholt/libepoxy/releases/tag/1.5.9



Signed-off-by: Adrian Perez de Castro <aperez@igalia.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>