command: add --osd-on-seek option defaulting to bar

Restores behaviour prior to aef2ed5dc1.

That change was apparently unpopular. However, given the amount of
complaining over how hard it is to change the defaults by rebinding every
key, I think the extra option introduced by this commit is justified.

Technically not all behaviour is restored, because now --no-osd-bar will
not instead display the msg text on seek. I think that feature was a
little weird and is now easy enough to remedy with the --osd-on-seek
option.

options/options.c

@@ -589,6 +589,11 @@ const m_option_t mp_opts[] = {
     OPT_FLAG("use-filedir-conf", use_filedir_conf, 0),
     OPT_CHOICE("osd-level", osd_level, 0,
                ({"0", 0}, {"1", 1}, {"2", 2}, {"3", 3})),
+    OPT_CHOICE("osd-on-seek", osd_on_seek, 0,
+               ({"no", 0},
+                {"bar", 1},
+                {"msg", 2},
+                {"msg-bar", 3})),
     OPT_INTRANGE("osd-duration", osd_duration, 0, 0, 3600000),
     OPT_FLAG("osd-fractions", osd_fractions, 0),
 
@@ -878,6 +883,7 @@ const struct MPOpts mp_default_opts = {
     .cursor_autohide_delay = 1000,
     .video_osd = 1,
     .osd_level = 1,
+    .osd_on_seek = 1,
     .osd_duration = 1000,
 #if HAVE_LUA
     .lua_load_osc = 1,

options/options.h

@@ -183,6 +183,7 @@ typedef struct MPOpts {
     int osd_level;
     int osd_duration;
     int osd_fractions;
+    int osd_on_seek;
     int video_osd;
 
     int untimed;