ncurses 5.8 - patch 20110307

ncurses 5.8 - patch 20110307

+ revert changes to limit-checks from 20110122 (Debian #616711).
> minor type-cleanup of Ada95 binding (Nicolas Boulenguez):
+ corrected a minor sign error in a field of Low_Level_Field_Type, to
  conform to form.h.
+ replaced C_Int by Curses_Bool as return type for some callbacks, see
  fieldtype(3FORM).
+ modify samples/sample-explain.adb to provide explicit message when
  explain.txt is not found.