Convert ^G back to 7 when sent.

This technically fixes issue 137 which specifically asked for
"backslash", but backspace (^H) and tab (^I) along with CR (^M)
still do a different thing than they do on Atari keyboards.

Further, CTRL-Q and CTRL-S are used by SyncTERM for Quit and Menu
respectively, so someone expecting all the Atari "stuff" to work
will still be disappointed.

This is a general problem with non-PC emulation (ie: Prestel, Atari,
and Commodore) that really needs some kind of general solution.

src/syncterm/term.c

@@ -4696,6 +4696,10 @@ doterm(struct bbslist *bbs)
 			if (key && (cterm->emulation == CTERM_EMULATION_ATASCII)) {
                                 /* Translate keys to ATASCII */
 				switch (key) {
+					case 253: // Undo Unicode: Atascii beep -> ^G
+						ch[0] = 7;
+						conn_send(ch, 1, 0);
+						break;
 					case CIO_KEY_DOWN:
 						ch[0] = 29;
 						conn_send(ch, 1, 0);