Move DataTypes.h from Support to llvm-c to fix layering.

Support depends on llvm-c (a few typedefs, macros, etc - Types.h,
Disassembler.h, and TargetMachine.h.

This could be done the other way - those macros/typedefs/etc could be
moved into Support and used from llvm-c instead. If someone feels that's
a better direction to go, happy to discuss it/try it out/etc.

llvm-svn: 328065