Loop metadata hints at unrolling and vectorization. mergefunc shouldn't merge
when they're different since someone expressed the wish for the functions to
differ (yes we could also ignore metadata, but let's not be mean). This can
happen when running mergefunc 'early' (right after clang or another frontend
generates code) but shouldn't happen when running it 'late' (after optimizations
are run and loop metadata has been put to use).
This inadvertently happens in test/Transforms/LoopVectorize/X86/metadata-enable.ll
This patch doesn't fix all of mergefunc's handling of metadata, it simply makes
one case less broken and puts us closer to being able to use mergefunc.