configure: Make use of ncurses configurable

When ncurses is found the current build system will use it to build the
"noping" utility. However, that will create an automagic dependencies on
ncurses which is a problem for some distributions.

This commit adds the ability to control the ncurses usage:

 a) If the user calls "configure" like before nothing changes: Configure
    tries to find a suitable ncurses installation to build "noping". If
    not found build system will just skip building of "noping" utility.

 b) If the user calls "configure" with new "--with-ncurses" option,
    configure will now fail if no suitable ncurses installation was
    found.

 c) If the user calls "configure" with new "--without-ncurses" option, the
    build system will now skip building of "noping" utility and ncurses
    will not be used.

In addition, this commit also changes the way configure will detect
ncurses: Configure now tries to use pkg-config to find ncurses but still
falls back to previous legacy checks. This will add support for ncurses
installation built with "--with-termlib" which causes several symbols to
get moved from libncurses.so to libtinfo.so.