terminal: Tab should not output spaces, just move cursor

Emacs uses tab and backspace to move the cursor as well as the regular
cursor movement escape codes.  When it's less bytes than the escape code,
emacs will use a tab or tab + backspace to move the cursor forward.  The
effect is that as you're  moving around in the buffer, emacs will
(seemingly) randomly insert spaces and overwrite what's in the terminal.
Making tab just move the cursor as it should fixes this.

clients/terminal.c

@@ -1763,12 +1763,6 @@ handle_sgr(struct terminal *terminal, int code)
 static int
 handle_special_char(struct terminal *terminal, char c)
 {
-	union utf8_char *row;
-	struct attr *attr_row;
-	
-	row = terminal_get_row(terminal, terminal->row);
-	attr_row = terminal_get_attr_row(terminal, terminal->row);
-	
 	switch(c) {
 	case '\r':
 		terminal->column = 0;
@@ -1791,9 +1785,6 @@ handle_special_char(struct terminal *terminal, char c)
 		while (terminal->column < terminal->width) {
 			if (terminal->mode & MODE_IRM)
 				terminal_shift_line(terminal, +1);
-			row[terminal->column].byte[0] = ' ';
-			row[terminal->column].byte[1] = '\0';
-			attr_row[terminal->column] = terminal->curr_attr;
 			terminal->column++;
 			if (terminal->tab_ruler[terminal->column]) break;
 		}