Add version of 'getFileCharacteristic()' for FileIDs.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59669 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/SourceManager.h

@@ -453,7 +453,10 @@ public:
   SrcMgr::CharacteristicKind getFileCharacteristic(SourceLocation Loc) const {
     return getFIDInfo(getPhysicalLoc(Loc).getFileID())->getFileCharacteristic();
   }
-
+  SrcMgr::CharacteristicKind getFileCharacteristic(unsigned FileID) const {
+    return getFIDInfo(FileID)->getFileCharacteristic();
+  }
+  
   // Iterators over FileIDs.
   
   class fileid_iterator {