Merge MCELF.h into MCSymbolELF.h.

Now that we have a dedicated type for ELF symbol, these helper functions can
become member function of MCSymbolELF.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238864 91177308-0d34-0410-b5e6-96231b3b80d8
21 files changed