input: stop trying to read terminal input on EOF

Stop trying to read terminal input if a read attempt returns EOF. The
most important case where this matters is when someone runs the player
with stdin redirected from /dev/null and without specifying
--no-consolecontrols. This used to cause 100% CPU load while paused,
as select() would continuously trigger on stdin (the need for
--no-consolecontrols was not apparent to people with older mplayer
versions, as input reading was less efficient and latencies like
hardcoded sleeps kept CPU use well below 100%). Now this will only
cause a "Dead key input" error message.

mplayer.c

@@ -3798,8 +3798,9 @@ static void run_playloop(struct MPContext *mpctx)
 
 static int read_keys(void *ctx, int fd)
 {
-    getch2(ctx);
-    return MP_INPUT_NOTHING;
+    if (getch2(ctx))
+        return MP_INPUT_NOTHING;
+    return MP_INPUT_DEAD;
 }
 
 static bool attachment_is_font(struct demux_attachment *att)

osdep/getch2-win.c

@@ -158,11 +158,12 @@ static int getch2_internal(void)
 	return -1;
 }
 
-void getch2(struct mp_fifo *fifo)
+bool getch2(struct mp_fifo *fifo)
 {
     int r = getch2_internal();
     if (r >= 0)
 	mplayer_put_key(fifo, r);
+    return true;
 }
 
 void getch2_enable(void)

osdep/getch2.c

@@ -158,11 +158,17 @@ void get_screen_size(void){
 #endif
 }
 
-void getch2(struct mp_fifo *fifo)
+bool getch2(struct mp_fifo *fifo)
 {
     int retval = read(0, &getch2_buf[getch2_len], BUF_LEN-getch2_len);
+    /* Return false on EOF to stop running select() on the FD, as it'd
+     * trigger all the time. Note that it's possible to get temporary
+     * EOF on terminal if the user presses ctrl-d, but that shouldn't
+     * happen if the terminal state change done in getch2_enable()
+     * works.
+     */
     if (retval < 1)
-        return;
+        return retval;
     getch2_len += retval;
 
     while (getch2_len > 0 && (getch2_len > 1 || getch2_buf[0] != 27)) {
@@ -279,6 +285,7 @@ void getch2(struct mp_fifo *fifo)
             getch2_buf[i] = getch2_buf[len+i];
         mplayer_put_key(fifo, code);
     }
+    return true;
 }
 
 static int getch2_status=0;

osdep/getch2.h

@@ -24,6 +24,8 @@
 #ifndef MPLAYER_GETCH2_H
 #define MPLAYER_GETCH2_H
 
+#include <stdbool.h>
+
 #include "config.h"
 
 /* Screen size. Initialized by load_termcap() and get_screen_size() */
@@ -45,7 +47,7 @@ void getch2_disable(void);
 
 /* Read a character or a special key code (see keycodes.h) */
 struct mp_fifo;
-void getch2(struct mp_fifo *fifo);
+bool getch2(struct mp_fifo *fifo);
 
 #ifdef CONFIG_ICONV
 /**