Limit usage of extern to config.h globals

Prefer passing arguments to declaring external global variables.  The
only remaining usage of extern is for config.h variables which are
needed in st.c instead of x.c (where it is now included).

Signed-off-by: Devin J. Pohly <djpohly@gmail.com>

x.c

@@ -227,6 +227,8 @@ static char *opt_line  = NULL;
 static char *opt_name  = NULL;
 static char *opt_title = NULL;
 
+static int oldbutton = 3; /* button event on startup: 3 = release */
+
 void
 clipcopy(const Arg *dummy)
 {
@@ -1733,8 +1735,7 @@ cmessage(XEvent *e)
 			win.mode &= ~MODE_FOCUSED;
 		}
 	} else if (e->xclient.data.l[0] == xw.wmdeletewin) {
-		/* Send SIGHUP to shell */
-		kill(pid, SIGHUP);
+		ttyhangup();
 		exit(0);
 	}
 }
@@ -1755,6 +1756,7 @@ run(void)
 	int w = win.w, h = win.h;
 	fd_set rfd;
 	int xfd = XConnectionNumber(xw.dpy), xev, blinkset = 0, dodraw = 0;
+	int ttyfd;
 	struct timespec drawtimeout, *tv = NULL, now, last, lastblink;
 	long deltatime;
 
@@ -1774,7 +1776,7 @@ run(void)
 		}
 	} while (ev.type != MapNotify);
 
-	ttynew(opt_line, opt_io, opt_cmd);
+	ttyfd = ttynew(opt_line, shell, opt_io, opt_cmd);
 	cresize(w, h);
 
 	clock_gettime(CLOCK_MONOTONIC, &last);
@@ -1782,15 +1784,15 @@ run(void)
 
 	for (xev = actionfps;;) {
 		FD_ZERO(&rfd);
-		FD_SET(cmdfd, &rfd);
+		FD_SET(ttyfd, &rfd);
 		FD_SET(xfd, &rfd);
 
-		if (pselect(MAX(xfd, cmdfd)+1, &rfd, NULL, NULL, tv, NULL) < 0) {
+		if (pselect(MAX(xfd, ttyfd)+1, &rfd, NULL, NULL, tv, NULL) < 0) {
 			if (errno == EINTR)
 				continue;
 			die("select failed: %s\n", strerror(errno));
 		}
-		if (FD_ISSET(cmdfd, &rfd)) {
+		if (FD_ISSET(ttyfd, &rfd)) {
 			ttyread();
 			if (blinktimeout) {
 				blinkset = tattrset(ATTR_BLINK);
@@ -1834,7 +1836,7 @@ run(void)
 
 			if (xev && !FD_ISSET(xfd, &rfd))
 				xev--;
-			if (!FD_ISSET(cmdfd, &rfd) && !FD_ISSET(xfd, &rfd)) {
+			if (!FD_ISSET(ttyfd, &rfd) && !FD_ISSET(xfd, &rfd)) {
 				if (blinkset) {
 					if (TIMEDIFF(now, lastblink) \
 							> blinktimeout) {