text.dat string IDs can now be used in/as @-codes, directly

The TEXT:<x> @-code can now be used with the text.dat string ID rather than
the text.dat string number, if preferred.

For convenience and brevity, ALL text.dat string IDs are now valid @-codes
(case-sensitive). While this functionality is redundant with the TEXT: @-code
now, if there are any conflicts between new/existing @-codes and text.dat
string IDs, the TEXT: @-code can be used to overcome such conflicts.

This should help with localization (to other languages) by using common
single-word replacements (Which, Quit, Next, etc.) in text.dat strings.

src/sbbs3/atcodes.cpp

@@ -918,7 +918,8 @@ const char* sbbs_t::atcode(char* sp, char* str, size_t maxlen, int* pmode, bool
 		i = atoi(sp + 5);
 		if(i >= 1 && i <= TOTAL_TEXT)
 			return text[i - 1];
-		return nulstr;
+		else
+			return gettext(sp + 5);
 	}
 
 	/* NOSTOP */
@@ -2188,6 +2189,5 @@ const char* sbbs_t::atcode(char* sp, char* str, size_t maxlen, int* pmode, bool
 		}
 	}
 
-	return NULL;
+	return gettext(sp);
 }
-