remove unnecessary volatiles

* ext/dbm/dbm.c (fdbm_initialize): used for rb_sys_fail_str.

* ext/sdbm/init.c (fsdbm_initialize): ditto.

* ext/tk/tcltklib.c (lib_do_one_event_core): no effect.

* ext/tk/tkutil/tkutil.c (tk_eval_cmd, tk_get_eval_string): no
  effect if tail call optimized.

* ext/tk/tkutil/tkutil.c (cbsubst_table_setup): set to const.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55127 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/dbm/dbm.c

@@ -145,8 +145,7 @@ fdbm_alloc(VALUE klass)
 static VALUE
 fdbm_initialize(int argc, VALUE *argv, VALUE obj)
 {
-    volatile VALUE file;
-    VALUE vmode, vflags;
+    VALUE file, vmode, vflags;
     DBM *dbm;
     struct dbmdata *dbmp;
     int mode, flags = 0;

ext/sdbm/init.c

@@ -179,8 +179,7 @@ fsdbm_alloc(VALUE klass)
 static VALUE
 fsdbm_initialize(int argc, VALUE *argv, VALUE obj)
 {
-    volatile VALUE file;
-    VALUE vmode;
+    VALUE file, vmode;
     DBM *dbm;
     struct dbmdata *dbmp;
     int mode;

ext/tk/tcltklib.c

@@ -3035,7 +3035,7 @@ lib_do_one_event_core(argc, argv, self, is_ip)
     VALUE self;
     int   is_ip;
 {
-    volatile VALUE vflags;
+    VALUE vflags;
     int flags;
     int found_event;
 

ext/tk/tkutil/tkutil.c

@@ -187,7 +187,7 @@ tk_eval_cmd(argc, argv, self)
     VALUE argv[];
     VALUE self;
 {
-    volatile VALUE cmd, rest;
+    VALUE cmd, rest;
 
     rb_scan_args(argc, argv, "1*", &cmd, &rest);
     return rb_eval_cmd(cmd, rest, 0);
@@ -952,7 +952,7 @@ tk_get_eval_string(argc, argv, self)
     VALUE *argv;
     VALUE self;
 {
-    volatile VALUE obj, enc_flag;
+    VALUE obj, enc_flag;
 
     if (rb_scan_args(argc, argv, "11", &obj, &enc_flag) == 1) {
         enc_flag = Qnil;
@@ -1563,7 +1563,7 @@ cbsubst_table_setup(argc, argv, self)
      VALUE *argv;
      VALUE self;
 {
-  volatile VALUE cbsubst_obj;
+  VALUE cbsubst_obj;
   VALUE key_inf;
   VALUE longkey_inf;
   VALUE proc_inf;