+ increase size of array in _nc_visbuf2n() to make "tic -v" work
properly in its similar_sgr() function (report/analysis by Peter
Santoro).
+ add --enable-reentrant configure option for ongoing changes to
implement a reentrant version of ncurses:
+ libraries are suffixed with "t"
+ wrap several global variables (curscr, newscr, stdscr, ttytype,
COLORS, COLOR_PAIRS, COLS, ESCDELAY, LINES and TABSIZE) as
functions returning values stored in SCREEN or cur_term.
+ move some initialization (LINES, COLS) from lib_setup.c,
i.e., setupterm() to _nc_setupscreen(), i.e., newterm().