Document ABIType enum. Patch by Sandeep Patel!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73427 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetMachine.h

@@ -78,6 +78,9 @@ namespace CodeGenOpt {
   };
 }
 
+
+// Possible float ABI settings. Soft is soft float, Hard is hard float, Default
+// is target-specific. Used with FloatABIType in TargetOptions.h.
 namespace FloatABI {
   enum ABIType {
     Default,