[CMake] --enable-* with cmake

[gga]

I'm currently using cmake for a variety of projects.  Love it.
However, one feature I find myself missing more and more is one from
autotools configure scripts: AC_ARG_ENABLE().
That is, the ability to allow the configuration script (ie. cmake) to be
run with arbitrary flags to turn on or turn off some options
(--enable-X11 for example), regardless of what it finds on the standard
paths.  Also this option in autoconf allows too have those options
available to the user thru a simple help line.

I know I can pass -D symbols to cmake to modify its behavior and that
windows also has its ugly CmakeSetup gui.

However, neither approach seems to me as clean as what's available under
autotools.  I'm wondering if I have missed something obvious or is there
some other approach to achieve the same functionality as autotools.



-- 
Gonzalo Garramuño
ggarra at advancedsl.com.ar

AMD4400 - ASUS48N-E
GeForce7300GT
Kubuntu Edgy