[ms] [llvm-ml] Implement the statement expansion operator

If prefaced with a %, expand text macros and macro functions in any statement.

Also, prevent expanding text macros in the message of an ECHO directive unless expanded explicitly by the statement expansion operator.

Reviewed By: thakis

Differential Revision: https://reviews.llvm.org/D89740

Author: ericastor

llvm/include/llvm/MC/MCAsmMacro.h

@@ -144,13 +144,15 @@ struct MCAsmMacro {
   StringRef Body;
   MCAsmMacroParameters Parameters;
   std::vector<std::string> Locals;
+  bool IsFunction = false;
 
 public:
   MCAsmMacro(StringRef N, StringRef B, MCAsmMacroParameters P)
       : Name(N), Body(B), Parameters(std::move(P)) {}
   MCAsmMacro(StringRef N, StringRef B, MCAsmMacroParameters P,
-             std::vector<std::string> L)
-      : Name(N), Body(B), Parameters(std::move(P)), Locals(std::move(L)) {}
+             std::vector<std::string> L, bool F)
+      : Name(N), Body(B), Parameters(std::move(P)), Locals(std::move(L)),
+        IsFunction(F) {}
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   void dump() const { dump(dbgs()); }