Fixes the following build issue with gcc >= 5.x

 In file included from ../ncurses/curses.priv.h:283:0,
                  from ../ncurses/lib_gen.c:19:
 _553.c:835:15: error: expected ')' before 'int'
 ../include/curses.h:1594:56: note: in definition of macro 'mouse_trafo'
  #define mouse_trafo(y,x,to_screen) wmouse_trafo(stdscr,y,x,to_screen)
                                                         ^

--- ncurses/base/MKlib_gen.sh
+++ ncurses/base/MKlib_gen.sh
@@ -62,7 +62,7 @@
 if test "${LC_CTYPE+set}"    = set; then LC_CTYPE=C;    export LC_CTYPE;    fi
 if test "${LC_COLLATE+set}"  = set; then LC_COLLATE=C;  export LC_COLLATE;  fi
 
-preprocessor="$1 -DNCURSES_INTERNALS -I../include"
+preprocessor="$1 -P -DNCURSES_INTERNALS -I../include"
 AWK="$2"
 USE="$3"