avcodec/libzvbi-teletextdec: fix txt_default_region limits

Max region ID is 87. Also the region affects not only the G0 charset but G2 and
the national subset as well.
Signed-off-by: Marton Balint <cus@passwd.hu>
(cherry picked from commit 16d29c1be80eda9ab5e2fb92b9cd300a88e5d449)

doc/decoders.texi

@@ -317,7 +317,7 @@ list are dropped. You may use the special @code{*} string to match all pages,
 or @code{subtitle} to match all subtitle pages.
 Default value is *.
 @item txt_default_region
-Set default G0 character set used for decoding, a value between 0 and 80 (see
+Set default character set used for decoding, a value between 0 and 87 (see
 ETS 300 706, Section 15, Table 32). Default value is -1, which does not
 override the libzvbi default. This option is needed for some legacy level 1.0
 transmissions which cannot signal the proper charset.

libavcodec/libzvbi-teletextdec.c

@@ -797,7 +797,7 @@ static void teletext_flush(AVCodecContext *avctx)
 #define SD AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM
 static const AVOption options[] = {
     {"txt_page",        "page numbers to decode, subtitle for subtitles, * for all", OFFSET(pgno),   AV_OPT_TYPE_STRING, {.str = "*"},      0, 0,        SD},
-    {"txt_default_region", "default G0 character set used for decoding",     OFFSET(default_region), AV_OPT_TYPE_INT,    {.i64 = -1},      -1, 80,       SD},
+    {"txt_default_region", "default G0 character set used for decoding",     OFFSET(default_region), AV_OPT_TYPE_INT,    {.i64 = -1},      -1, 87,       SD},
     {"txt_chop_top",    "discards the top teletext line",                    OFFSET(chop_top),       AV_OPT_TYPE_INT,    {.i64 = 1},        0, 1,        SD},
     {"txt_format",      "format of the subtitles (bitmap or text or ass)",   OFFSET(format_id),      AV_OPT_TYPE_INT,    {.i64 = 0},        0, 2,        SD,  "txt_format"},
     {"bitmap",          NULL,                                                0,                      AV_OPT_TYPE_CONST,  {.i64 = 0},        0, 0,        SD,  "txt_format"},