Fix Casting

Make the const_cast explicit to silence a compiler warning.

llvm-svn: 172560

clang/lib/Serialization/ASTWriter.cpp

@@ -1552,7 +1552,7 @@ void ASTWriter::WriteHeaderSearch(const HeaderSearch &HS, StringRef isysroot) {
   
   // Free all of the strings we had to duplicate.
   for (unsigned I = 0, N = SavedStrings.size(); I != N; ++I)
-    free((void*)SavedStrings[I]);
+    free(const_cast<char *>(SavedStrings[I]));
 }
 
 /// \brief Writes the block containing the serialized form of the