[clang] [clang-repl] adding documentation and information for %commands (PR #150348)

[David Spickett via cfe-commits]

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@@ -28,6 +28,7 @@
 #include "llvm/Support/ManagedStatic.h" // llvm_shutdown
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/raw_ostream.h"
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DavidSpickett wrote:

If we leave the welcome message out, you can remove this.

https://github.com/llvm/llvm-project/pull/150348