build: show configure summary using a pretty format

[rbuj]

sample output:

Configure summary:

    mate-screensaver 1.26.0
    =======================

    prefix .......................: /usr
    exec_prefix ..................: ${prefix}
    libdir .......................: /usr/lib64
    bindir .......................: /usr/bin
    sysconfdir ...................: /etc
    localstatedir ................: /var
    datadir ......................: ${prefix}/share
    PAM prefix ...................: /etc
    source code location .........: .
    compiler .....................: gcc
    cflags .......................: 
    Warning flags ................: -Wall -Wmissing-prototypes
    Base libs ....................: -lX11 -lXss -ldbus-glib-1 -ldbus-1 -lmate-desktop-2 -lgtk-3 -lgdk-3 -lpangocairo-1.0 -lpango-1.0 -lharfbuzz -latk-1.0 -lcairo-gobject -lcairo -lgdk_pixbuf-2.0 -lstartup-notification-1 -lmate-menu -lgio-2.0 -lgobject-2.0 -lglib-2.0 
    Extension libs ...............:   -lSM -lICE -lXext -lX11  -lXss -lXxf86vm
    Maintainer mode ..............: yes
    Docs enabled .................: no

    GL ...........................: yes

    Screen locking enabled .......: yes
    Show keyboard indicator ......: yes
    systemd support ..............: yes
    elogind support ..............: no
    ConsoleKit support ...........: yes
    libnotify support ............: yes
    PAM support ..................: yes
    bsd_auth(3) support ..........: no
    Have shadow passwords ........: yes
    Have adjunct shadow ..........: no
    Have enhanced shadow .........: no
    Have HPUX shadow .............: no
    Have password helper .........: no
    Authentication scheme ........: pam
    Need setuid dialog ...........: no

Now type `make' to compile mate-screensaver