Move anchor() to implementation file

Author: tblah

mlir/include/mlir/Support/StateStack.h

@@ -32,7 +32,7 @@ class StateStackFrame {
 
 private:
   const TypeID typeID;
-  virtual void anchor() {};
+  virtual void anchor();
 };
 
 /// Concrete CRTP base class for StateStack frames. This is used for keeping a

mlir/lib/Support/StateStack.cpp

@@ -7,3 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Support/StateStack.h"
+
+namespace mlir {
+
+void StateStackFrame::anchor() {}
+
+} // namespace mlir