Switch all uses of LLVM_OVERRIDE to just use 'override' directly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202621 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/DataStream.cpp

@@ -58,7 +58,7 @@ public:
   virtual ~DataFileStreamer() {
     close(Fd);
   }
-  virtual size_t GetBytes(unsigned char *buf, size_t len) LLVM_OVERRIDE {
+  virtual size_t GetBytes(unsigned char *buf, size_t len) override {
     NumStreamFetches++;
     return read(Fd, buf, len);
   }