Add Atari ST VT52 modes

src/conio/allfonts.c

src/conio/ciolib.adoc

src/conio/ciolib.c

src/conio/ciolib.h

src/conio/cterm.c

src/conio/cterm.h

src/conio/utf8_codepages.c

src/conio/utf8_codepages.h

src/conio/vidmodes.c

src/conio/vidmodes.h

src/syncterm/CHANGES

src/syncterm/bbslist.c

src/syncterm/bbslist.h

src/syncterm/syncterm.c

src/syncterm/term.c