ncurses 5.6 - patch 20070310

ncurses 5.6 - patch 20070310

+ 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().