fix gbsinfo crash with many subsongs

See bug report at http://www.forallsecure.com/bug-reports/e917758134cc7d0f48ca0af77fcad861f1d36aa9/
252 subsongs got parsed as a negative number which made aus malloc() a negative amount of memory...

fix:
change data types of gbs.version, gbs.songs and gbs.dafaultsong from long to uint8_t
add default subsong to gbsinfo output

now we'll have to update translations!
fix -Wformat-security warnings in plugout.c

plugout.c: In function ‘plugout_list_plugins’:
plugout.c:58:2: warning: format not a string literal and no format arguments [-Wformat-security]
plugout.c:61:3: warning: format not a string literal and no format arguments [-Wformat-security]

I could have used puts(_("")); instead of printf("%s", _("")); but
that would have resulted in an extra newline and all translations
would have to be changed.