[msan] Remove icmp tests that require exact shadow propagation.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@173686 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] A runtime call to support custom allocators.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@173687 91177308-0d34-0410-b5e6-96231b3b80d8