Instead of combined flags for -c, -s, -t, split into different sets

using an enum and simplify the parsing code.

cmd-break-pane.c

@@ -37,7 +37,10 @@ const struct cmd_entry cmd_break_pane_entry = {
 	.args = { "dPF:s:t:", 0, 0 },
 	.usage = "[-dP] [-F format] " CMD_SRCDST_PANE_USAGE,
 
-	.flags = CMD_PANE_S|CMD_INDEX_T,
+	.sflag = CMD_PANE,
+	.tflag = CMD_WINDOW_INDEX,
+
+	.flags = 0,
 	.exec = cmd_break_pane_exec
 };