Revert "TargetMachine: Merge TargetMachine and LLVMTargetMachine"

Reverting to investigate layering effects of MCJIT not linking
libCodeGen but using TargetMachine::getNameWithPrefix() breaking the
lldb bots.

This reverts commit r315633.

llvm-svn: 315637
diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.h b/llvm/lib/Target/PowerPC/PPCTargetMachine.h
index d3be1ee..102bf7c 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.h
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.h
@@ -23,7 +23,7 @@
 
 /// Common code between 32-bit and 64-bit PowerPC targets.
 ///
-class PPCTargetMachine final : public TargetMachine {
+class PPCTargetMachine final : public LLVMTargetMachine {
 public:
   enum PPCABI { PPC_ABI_UNKNOWN, PPC_ABI_ELFv1, PPC_ABI_ELFv2 };
 private: