Merging r181366:

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r181366 | enderby | 2013-05-07 14:40:58 -0700 (Tue, 07 May 2013) | 6 lines

Fix a bug in the MC asm parser evaluating expressions.  It was treating:
A = 9
B = 3 * A - 2 * A + 1 as  B = 3 * A - (2 * A + 1)

rdar://13816516

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_33@182438 91177308-0d34-0410-b5e6-96231b3b80d8