[lldb][NFC] Remove forward declaration for non-existent type clang::Action and delete references to it

There is no clang::Action anymore so our forward decl for it and the obsolete pointer in the
ASTStructExtractor can both go (that code anyway didn't do anything).

Author: Teemperor

lldb/include/lldb/Core/ClangForward.h

@@ -17,7 +17,6 @@ namespace Builtin {
 class Context;
 }
 
-class Action;
 class ASTConsumer;
 class ASTContext;
 class ASTRecordLayout;

lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.cpp

@@ -30,8 +30,8 @@ ASTStructExtractor::ASTStructExtractor(ASTConsumer *passthrough,
                                        const char *struct_name,
                                        ClangFunctionCaller &function)
     : m_ast_context(nullptr), m_passthrough(passthrough),
-      m_passthrough_sema(nullptr), m_sema(nullptr), m_action(nullptr),
-      m_function(function), m_struct_name(struct_name) {
+      m_passthrough_sema(nullptr), m_sema(nullptr), m_function(function),
+      m_struct_name(struct_name) {
   if (!m_passthrough)
     return;
 
@@ -170,15 +170,13 @@ void ASTStructExtractor::PrintStats() {
 
 void ASTStructExtractor::InitializeSema(Sema &S) {
   m_sema = &S;
-  m_action = reinterpret_cast<Action *>(m_sema);
 
   if (m_passthrough_sema)
     m_passthrough_sema->InitializeSema(S);
 }
 
 void ASTStructExtractor::ForgetSema() {
   m_sema = nullptr;
-  m_action = nullptr;
 
   if (m_passthrough_sema)
     m_passthrough_sema->ForgetSema();

lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.h

@@ -121,8 +121,6 @@ class ASTStructExtractor : public clang::SemaConsumer {
                                            ///for passthrough.  NULL if it's an
                                            ///ASTConsumer.
   clang::Sema *m_sema;                     ///< The Sema to use.
-  clang::Action
-      *m_action; ///< The Sema to use, cast to an Action so it's usable.
 
   ClangFunctionCaller &m_function; ///< The function to populate with
                                    ///information about the argument structure.