+20080531
+ + modify wgetch() to use the screen which corresponds to its window
+ parameter rather than relying on SP; some dependent functions still
+ use SP internally.
+ + factor out most use of SP in lib_mouse.c, using parameter.
+ + add internal _nc_keyname(), replacing keyname() to associate with a
+ particular SCREEN rather than the global SP.
+ + add internal _nc_unctrl(), replacing unctrl() to associate with a
+ particular SCREEN rather than the global SP.
+ + add internal _nc_tracemouse(), replacing _tracemouse() to eliminate
+ its associated global buffer _nc_globals.tracemse_buf now in SCREEN.
+ + add internal _nc_tracechar(), replacing _tracechar() to use SCREEN in
+ preference to the global _nc_globals.tracechr_buf buffer.
+
+20080524
+ + modify _nc_keypad() to make it switch temporarily as needed to the
+ screen which must be updated.
+ + wrap cur_term variable to help make _nc_keymap() thread-safe, and
+ always set the screen's copy of this variable in set_curterm().
+ + restore curs_set() state after endwin()/refresh() (report/patch
+ Miroslav Lichvar)
+