Add an option `-enable-old-style-attr-syntax' to print out function attributes in the "old" style.

It's sometimes beneficial to emit a testcase with the old style attribute
syntax. Allow someone to do this.
<rdar://problem/13563209>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179735 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Attributes.h

@@ -306,7 +306,8 @@ public:
   unsigned getStackAlignment(unsigned Index) const;
 
   /// \brief Return the attributes at the index as a string.
-  std::string getAsString(unsigned Index, bool InAttrGrp = false) const;
+  std::string getAsString(unsigned Index, bool TargetIndependent = false,
+                          bool InAttrGrp = false) const;
 
   typedef ArrayRef<Attribute>::iterator iterator;