Seems like glslang upstream is more than happy to make their patch level
go back down to 0 now. To handle the mishmash of old and new versioning
schemes, we map the old patch level to version 0.0.x, which ensures it's
forwards-compatible with the new versioning scheme (that was fortunately
introduced after every relevant check of ours).

Fixes https://github.com/haasn/libplacebo/issues/83 again, properly this
time.