Merging r196294:

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r196294 | arnolds | 2013-12-03 08:33:06 -0800 (Tue, 03 Dec 2013) | 7 lines

opt: Mirror vectorization presets of clang

clang enables vectorization at optimization levels > 1 and size level < 2. opt
should behave similarily.

Loop vectorization and SLP vectorization can be disabled with the flags
-disable-(loop/slp)-vectorization.
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llvm-svn: 196649