Prune some includes from headers and sink some inline functions

MCSymbol.h shouldn't pull in MCAssembler.h, just MCFragment.h.
MCLinkerOptimizationHint.h shouldn't need MCMachObjectWriter.h.  The
rest is fixing the fallout.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273507 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed