Revert "Re-commit r192758 - MC: quote tricky symbol names in asm output"

This caused the clang-native-mingw32-win7 buildbot to break.

The assembler was complaining about the following lines that were showing up
in the asm for CrashRecoveryContext.cpp:

  movl  $"__ZL16ExceptionHandlerP19_EXCEPTION_POINTERS@4", 4(%eax)
  calll "_AddVectoredExceptionHandler@8"
  .def   "__ZL16ExceptionHandlerP19_EXCEPTION_POINTERS@4";
  "__ZL16ExceptionHandlerP19_EXCEPTION_POINTERS@4":
  calll "_RemoveVectoredExceptionHandler@4"

Reverting for now.