Merging r181524:
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r181524 | rafael | 2013-05-09 10:22:59 -0700 (Thu, 09 May 2013) | 4 lines

Don't replace an alias in llvm.used with its target.

When we replace an internal alias with its target, be careful not to
replace the entry in llvm.used (and llvm.compiler_used).
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