Port Wayland clients to new xkbcommon API

A little different from Daniels initial patch.  We look up the common
modifiers at xkb init time and convert the xkb serialized modifier mask
to our own modifier bitmask.
diff --git a/clients/terminal.c b/clients/terminal.c
index 4fbc1ff..c8818d0 100644
--- a/clients/terminal.c
+++ b/clients/terminal.c
@@ -272,9 +272,9 @@
 	int mod_num = 0;
 	int len;
 
-	if (modifiers & XKB_COMMON_SHIFT_MASK) mod_num   |= 1;
-	if (modifiers & XKB_COMMON_MOD1_MASK) mod_num    |= 2;
-	if (modifiers & XKB_COMMON_CONTROL_MASK) mod_num |= 4;
+	if (modifiers & MOD_SHIFT_MASK) mod_num   |= 1;
+	if (modifiers & MOD_ALT_MASK) mod_num    |= 2;
+	if (modifiers & MOD_CONTROL_MASK) mod_num |= 4;
 
 	if (mod_num != 0)
 		len = snprintf(response, MAX_RESPONSE, "\e[%d;%d%c",
@@ -2078,8 +2078,8 @@
 	int len = 0;
 
 	modifiers = input_get_modifiers(input);
-	if ((modifiers & XKB_COMMON_CONTROL_MASK) &&
-	    (modifiers & XKB_COMMON_SHIFT_MASK) &&
+	if ((modifiers & MOD_CONTROL_MASK) &&
+	    (modifiers & MOD_SHIFT_MASK) &&
 	    state && handle_bound_key(terminal, input, sym, time))
 		return;
 
@@ -2173,7 +2173,7 @@
 		len = apply_key_map(terminal->key_mode, sym, modifiers, ch);
 		if (len != 0) break;
 		
-		if (modifiers & XKB_COMMON_CONTROL_MASK) {
+		if (modifiers & MOD_CONTROL_MASK) {
 			if (sym >= '3' && sym <= '7')
 				sym = (sym & 0x1f) + 8;
 
@@ -2184,10 +2184,10 @@
 			else if (sym == '/') sym = 0x1F;
 			else if (sym == '8' || sym == '?') sym = 0x7F;
 		} else if ((terminal->mode & MODE_ALT_SENDS_ESC) && 
-			   (modifiers & XKB_COMMON_MOD1_MASK))
+			   (modifiers & MOD_ALT_MASK))
 		{
 			ch[len++] = 0x1b;
-		} else if (modifiers & XKB_COMMON_MOD1_MASK) {
+		} else if (modifiers & MOD_ALT_MASK) {
 			sym = sym | 0x80;
 		}