Merging r286998:

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r286998 | chfast | 2016-11-15 19:29:24 +0100 (wto, 15 lis 2016) | 12 lines

Integer legalization: fix MUL expansion

Summary:
This fixes the runtime results produces by the fallback multiplication expansion introduced in r270720.

For tests I created a fuzz tester that compares the results with Boost.Multiprecision.

Reviewers: hfinkel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26628

llvm-svn: 288086