* xterm.c: Integer and memory overflow issues.

* xterm.c: Integer and memory overflow issues.

(x_color_cells, handle_one_xevent, x_term_init):
Check for size calculation overflow.
(x_color_cells): Don't store size until memory allocation succeeds.
(handle_one_xevent): Use ptrdiff_t, not int, for byte counts.
(x_term_init): Don't assume length fits in int (sprintf is limited
to int size).