locals: add locale for subtitles charset selection

data/locale/english.locale

@@ -1875,6 +1875,7 @@ streaming.slow System/hdd too slow, consider to stop some records
 streaming.write_error The recording was aborted,\nsince an error occured during the writing process.
 stringinput.caps caps / no caps
 stringinput.clear clear all
+subtitles.charset Charset
 subtitles.head Subtitles
 subtitles.stop Stop subtitles
 timer.eventrecord.msg The event is scheduled for recording.\nTo edit the schedule open the timer list.

src/system/locals.h

@@ -1902,6 +1902,7 @@ typedef enum
 	LOCALE_STREAMING_WRITE_ERROR,
 	LOCALE_STRINGINPUT_CAPS,
 	LOCALE_STRINGINPUT_CLEAR,
+	LOCALE_SUBTITLES_CHARSET,
 	LOCALE_SUBTITLES_HEAD,
 	LOCALE_SUBTITLES_STOP,
 	LOCALE_TIMER_EVENTRECORD_MSG,

src/system/locals_intern.h

@@ -1902,6 +1902,7 @@ const char * locale_real_names[] =
 	"streaming.write_error",
 	"stringinput.caps",
 	"stringinput.clear",
+	"subtitles.charset",
 	"subtitles.head",
 	"subtitles.stop",
 	"timer.eventrecord.msg",