ncurses 6.0 - patch 20151212

+ improve CF_XOPEN_CURSES macro used in test/configure, to define as
  needed NCURSES_WIDECHAR for platforms where _XOPEN_SOURCE_EXTENDED
  does not work.  Also modified the test program to ensure that if
  building with ncurses, that the cchar_t type is checked, since that
  normally is since 20111030 ifdef'd depending on this test.
+ improve 20121222 workaround for broken acs, letting Solaris "work"
  in spite of its m.isconfigured wcwidth which marks all of the line
  drawing characters as double-width.