Don't store AttributeSet::FunctionIndex as an int.

GCC complains: Core.cpp:1449:27: warning: overflow in implicit constant conversion [-Woverflow]
I'm not sure if that's really a problem here, but using the enum type is better
style anyways.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179696 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/Core.cpp

@@ -1446,7 +1446,7 @@ void LLVMAddFunctionAttr(LLVMValueRef Fn, LLVMAttribute PA) {
 void LLVMAddTargetDependentFunctionAttr(LLVMValueRef Fn, const char *A,
                                         const char *V) {
   Function *Func = unwrap<Function>(Fn);
-  int Idx = AttributeSet::FunctionIndex;
+  AttributeSet::AttrIndex Idx = AttributeSet::FunctionIndex;
   AttrBuilder B;
 
   B.addAttribute(A, V);