Object, COFF: Cleanup symbol type code, improve binutils compatibility

Do a better job classifying symbols.  This increases the consistency
between the COFF handling code and the ELF side of things.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220952 91177308-0d34-0410-b5e6-96231b3b80d8