Registry.h should not depend on CommandLine.h.

Split Support/Registry.h into two files so that we have less to
recompile every time CommandLine.h is changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62312 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/OcamlGC.cpp

@@ -16,6 +16,7 @@
 
 #include "llvm/CodeGen/GCs.h"
 #include "llvm/CodeGen/GCStrategy.h"
+#include "llvm/Support/Compiler.h"
 
 using namespace llvm;