[flang][NFC] Add debug dump method to evaluate::Expr and semantics::Symbol

Helps debugging when working with symbol/expression issue. The dump
method is easy to call in the debugger.

GitOrigin-RevId: b0e35fde21ecb47799603e1acfc9ffa7b83dea13
diff --git a/lib/Evaluate/expression.cpp b/lib/Evaluate/expression.cpp
index 576e330..1086619 100644
--- a/lib/Evaluate/expression.cpp
+++ b/lib/Evaluate/expression.cpp
@@ -18,6 +18,7 @@
 #include "flang/Semantics/symbol.h"
 #include "flang/Semantics/tools.h"
 #include "flang/Semantics/type.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/raw_ostream.h"
 #include <string>
 #include <type_traits>