ncurses 6.0 - patch 20150613

ncurses 6.0 - patch 20150613

+ fix overflow warning for OSX with lib_baudrate.c (cf: 20010630).
+ modify script used to generate map/sym files to mark 5.9.20150530 as
  the last "5.9" version, and regenerated the files.  That makes the
  files not use ".current" for the post-5.9 symbols.  This also
  corrects the label for _nc_sigprocmask used in when weak symbols are
  configured for the ncursest/ncursestw libraries (prompted by
  discussion with Sven Joachim).
+ fix typo in NEWS (report by Sven Joachim).
  "--with-abi-version=5" option.