Audit and replace all ctype.h uses

Something like "char *s = ...; isdigit(s[0]);" triggers undefined
behavior, because char can be signed, and thus s[0] can be a negative
value. The is*() functions require unsigned char _or_ EOF. EOF is a
special value outside of unsigned char range, thus the argument to the
is*() functions can't be a char.

This undefined behavior can actually trigger crashes if the
implementation of these functions e.g. uses lookup tables, which are
then indexed with out-of-range values.

Replace all <ctype.h> uses with our own custom mp_is*() functions added
with misc/ctype.h. As a bonus, these functions are locale-independent.
(Although currently, we _require_ C locale for other reasons.)

stream/dvb_tune.c

@@ -25,7 +25,6 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <ctype.h>
 #include <sys/ioctl.h>
 #include <poll.h>
 #include <unistd.h>

stream/stream_dvb.c

@@ -34,7 +34,6 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <ctype.h>
 #include <sys/ioctl.h>
 #include <sys/time.h>
 #include <poll.h>
@@ -45,6 +44,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 #include <libavutil/avstring.h>
 
 #include "osdep/io.h"
+#include "misc/ctype.h"
 
 #include "stream.h"
 #include "options/m_config.h"
@@ -177,7 +177,7 @@ static dvb_channels_list *dvb_get_channels(struct mp_log *log, char *filename, i
                 {
                         fields = sscanf(&line[k], sat_conf,
                                 &ptr->freq, &ptr->pol, &ptr->diseqc, &ptr->srate, vpid_str, apid_str);
-                        ptr->pol = toupper(ptr->pol);
+                        ptr->pol = mp_toupper(ptr->pol);
                         ptr->freq *=  1000UL;
                         ptr->srate *=  1000UL;
                         ptr->tone = -1;

stream/stream_dvd.c

@@ -18,7 +18,6 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

stream/stream_pvr.c

@@ -30,7 +30,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
-#include <ctype.h>
 #include <sys/time.h>
 #include <errno.h>
 #include <sys/ioctl.h>

stream/tv.c

@@ -29,7 +29,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
-#include <ctype.h>
 #include <sys/time.h>
 #include <assert.h>
 #include <libavutil/avstring.h>
@@ -38,6 +37,7 @@
 
 
 #include "common/msg.h"
+#include "misc/ctype.h"
 
 #include "options/m_option.h"
 #include "options/m_config.h"
@@ -628,7 +628,7 @@ static int open_tv(tvi_handle_t *tvh)
         int channel = 0;
         if (tvh->tv_param->channel)
          {
-           if (isdigit(*tvh->tv_param->channel))
+           if (mp_isdigit(*tvh->tv_param->channel))
                 /* if tvh->tv_param->channel begins with a digit interpret it as a number */
                 channel = atoi(tvh->tv_param->channel);
            else