ncurses: Fix build of libncursew

ncurses: Fix build of libncursew

Packages using libncursesw can fail to build if both libncurses and libncursesw
are not installed. Currently the ncurses.h file is installed in "usr/include/ncursesw"
directory and includes other .h files in the "usr/include" directory incorrectly.
For example: Including <ncursesw/ncurses.h> fails due to these references. These build
changes will set the correct include paths within the developer includes.

Packages that expect ncurses.h (or curses.h) in the default "usr/include" path fail
even when expecting to build with libncursesw and will need to be fixed as well. However,
they cannot be fixed until this patch is applied.

Signed-off-by: Ted Hess <thess@kitschensync.net>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47853 3c298f89-4303-0410-b956-a3cf2f4a3e73