Fix GCC warnings:

 hex escape sequence out of range

src/sbbs3/atcodes.cpp

@@ -196,11 +196,11 @@ const char* sbbs_t::atcode(char* sp, char* str, size_t maxlen)
 		return nulstr;
 	}
 	if(strcmp(sp, "DEGREE_C") == 0) {
-		outchar(UNICODE_DEGREE_CELSIUS, "\xF8C");
+		outchar(UNICODE_DEGREE_CELSIUS, "\xF8""C");
 		return nulstr;
 	}
 	if(strcmp(sp, "DEGREE_F") == 0) {
-		outchar(UNICODE_DEGREE_FAHRENHEIT, "\xF8F");
+		outchar(UNICODE_DEGREE_FAHRENHEIT, "\xF8""F");
 		return nulstr;
 	}