Rename loop unrolling and loop vectorizer metadata to have a common prefix.

[LLVM part]

These patches rename the loop unrolling and loop vectorizer metadata
such that they have a common 'llvm.loop.' prefix.  Metadata name
changes:

llvm.vectorizer.* => llvm.loop.vectorizer.*
llvm.loopunroll.* => llvm.loop.unroll.*

This was a suggestion from an earlier review
(http://reviews.llvm.org/D4090) which added the loop unrolling
metadata. 

Patch by Mark Heffernan.

llvm-svn: 211710
diff --git a/llvm/test/Transforms/LoopVectorize/metadata-width.ll b/llvm/test/Transforms/LoopVectorize/metadata-width.ll
index 1960c0b..87de655 100644
--- a/llvm/test/Transforms/LoopVectorize/metadata-width.ll
+++ b/llvm/test/Transforms/LoopVectorize/metadata-width.ll
@@ -28,4 +28,4 @@
 attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
 !0 = metadata !{metadata !0, metadata !1}
-!1 = metadata !{metadata !"llvm.vectorizer.width", i32 8}
+!1 = metadata !{metadata !"llvm.loop.vectorize.width", i32 8}