Build with static libs from most recent source distribution. Since we
want a click-and-working installer, it's not effordable to request
installing X11 (10.4) or similar.
1) From X11. Seems to be the most simple way.
2) From most recent source distribution. Where to install? Maybe:
Static linkage against libraries built and installed in the mpl build
dir. This would avoid overwriting the user's system-wide libraries.
It would also have the advantage to support non-root builds.
3) From binary distribution package including just those libraries.
This seems not a bright idea.
4) From separately user-compiled and system wide installed source
distributions of the libraries.
10.4: Looks like that X11 has to be opted in. (John)
10.6: X11 very much probably included (opt-out at OS install point).
Installed in /usr/X11/lib/. (Friedrich)
=> A build system should detect the native OS X libraries (way (1)).
If they are not present, it's up to the user to decide what to do, if
to go route (2), (3), or (4). Build system could use Paver (as numpy