Removed dead code from clang/AST/NSAPI.h

clang/include/clang/AST/NSAPI.h

public:
   };
   static const unsigned NumNSStringMethods = 6;
 
   IdentifierInfo *getNSClassId(NSClassIdKindKind K) const;
 
   /// The Objective-C NSString selectors.
   Selector getNSStringSelector(NSStringMethodKind MK) const;
 
-  /// Return NSStringMethodKind if \param Sel is such a selector.
-  Optional<NSStringMethodKind> getNSStringMethodKind(Selector Sel) const;
-
   /// Returns true if the expression \param E is a reference of
   /// "NSUTF8StringEncoding" enum constant.
   bool isNSUTF8StringEncodingConstant(const Expr *E) const {
     return isObjCEnumerator(E, "NSUTF8StringEncoding", NSUTF8StringEncodingId);
   }
 
   /// Returns true if the expression \param E is a reference of
   /// "NSASCIIStringEncoding" enum constant.

clang/lib/AST/NSAPI.cpp

case NSStr_initWithString:
       break;
     }
     return (NSStringSelectors[MK] = Sel);
   }
 
   return NSStringSelectors[MK];
 }
 
-Optional<NSAPI::NSStringMethodKind>
-NSAPI::getNSStringMethodKind(Selector Sel) const {
-  for (unsigned i = 0; i != NumNSStringMethods; ++i) {
-    NSStringMethodKind MK = NSStringMethodKind(i);
-    if (Sel == getNSStringSelector(MK))
-      return MK;
-  }
-
-  return None;
-}
-
 Selector NSAPI::getNSArraySelector(NSArrayMethodKind MK) const {
   if (NSArraySelectors[MK].isNull()) {
     Selector Sel;
     switch (MK) {
     case NSArr_array:
       Sel = Ctx.Selectors.getNullarySelector(&Ctx.Idents.get("array"));
       break;
     case NSArr_arrayWithArray: