[msan] Fix __msan_check_mem_is_initialized and prettify its output.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@208195 91177308-0d34-0410-b5e6-96231b3b80d8
[sanitizer] Intercept obstack.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@208196 91177308-0d34-0410-b5e6-96231b3b80d8