[msan] Precise origin handling in __unaligned_(load|store)*.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@205412 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Add __msan_check_mem_is_initialized.

An assert()-like function that checks that a memory range is fully initialized.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@205413 91177308-0d34-0410-b5e6-96231b3b80d8