config.def.h: make keys and buttons const

pretty much all other variables are declared as const when they're not
modified.

config.def.h

@@ -59,7 +59,7 @@ static char dmenumon[2] = "0"; /* component of dmenucmd, manipulated in spawn()
 static const char *dmenucmd[] = { "dmenu_run", "-m", dmenumon, "-fn", dmenufont, "-nb", col_gray1, "-nf", col_gray3, "-sb", col_cyan, "-sf", col_gray4, NULL };
 static const char *termcmd[]  = { "st", NULL };
 
-static Key keys[] = {
+static const Key keys[] = {
 	/* modifier                     key        function        argument */
 	{ MODKEY,                       XK_p,      spawn,          {.v = dmenucmd } },
 	{ MODKEY|ShiftMask,             XK_Return, spawn,          {.v = termcmd } },
@@ -98,7 +98,7 @@ static Key keys[] = {
 
 /* button definitions */
 /* click can be ClkTagBar, ClkLtSymbol, ClkStatusText, ClkWinTitle, ClkClientWin, or ClkRootWin */
-static Button buttons[] = {
+static const Button buttons[] = {
 	/* click                event mask      button          function        argument */
 	{ ClkLtSymbol,          0,              Button1,        setlayout,      {0} },
 	{ ClkLtSymbol,          0,              Button3,        setlayout,      {.v = &layouts[2]} },