Revert layering changes

This reverts:
  r328072 "Move Compiler.h from Support to Demangler to fix layering."
  r328073 "Fix the actual user of DataTypes.h in llvm-c to avoid the circular dependency"

Failing bots:
  http://green.lab.llvm.org/green/job/clang-stage2-coverage-R/
  http://green.lab.llvm.org/green/job/clang-stage2-configure-Rlto/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328085 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed