ncurses 6.1 - patch 20180526

+ add note in curs_util.3x about unctrl.h
+ review/improve header files to ensure that those include necessary
  files except for the previously-documented cases (report by Isaac
  Pascual Monells).
+ improved test-package scripts, adapted from byacc 1.9 20180525.
+ fix some gcc8 warnings seen in Redhat package build, but
  work around bug in gcc8 compiler warnings in comp_parse.c