avoid including symtab.h, symscope.h, or symrec.h unnecessarily * main-window.cc, workspace-view.cc, call-stack.cc, call-stack.h, defun-int.h, input.cc, load-save.h, symscope.h, symtab.h, variables.h, ov-fcn-inline.h, ov-fcn.h, ov-usr-fcn.cc, ov-usr-fcn.h, lex.h, oct-lvalue.h, parse.h, pt-arg-list.h, pt-array-list.h, pt-assign.h, pt-binop.h, pt-cbinop.h, pt-cell.h, pt-cmd.h, pt-colon.h, pt-const.h, pt-decl.h, pt-eval.h, pt-except.h, pt-exp.h, pt-fcn-handle.h, pt-idx.h, pt-jit.h, pt-jump.h, pt-loop.h, pt-mat.h, pt-misc.h, pt-select.h, pt-stmt.h, pt-unop.h, token.cc, token.h: Where possible, use forward declarations for symbol_table, symbol_scope, and symbol_record. Don't include symtab.h, symscope.h, or symrec.h unless needed. Use symbol_record::context_id instead of symbol_table::context_id or symbol_scope::context_id. Delete typedefs for symbol_table::context_id and symbol_scope::context_id.

--- a/libinterp/parse-tree/pt-arg-list.h	Mon Nov 27 01:12:05 2017 -0500
+++ b/libinterp/parse-tree/pt-arg-list.h	Tue Dec 05 17:09:24 2017 -0500
@@ -27,16 +27,17 @@
 
 #include <list>
 
+class octave_value;
 class octave_value_list;
 
 #include "str-vec.h"
 
 #include "base-list.h"
 #include "pt-walk.h"
-#include "symtab.h"
 
 namespace octave
 {
+  class symbol_scope;
   class tree_evaluator;
   class tree_expression;
 
@@ -89,8 +90,9 @@
 
     bool is_valid_lvalue_list (void) const;
 
-    octave_value_list convert_to_const_vector (tree_evaluator *tw,
-                                               const octave_value *object = nullptr);
+    octave_value_list
+    convert_to_const_vector (tree_evaluator *tw,
+                             const octave_value *object = nullptr);
 
     string_vector get_arg_names (void) const;