zip up large libraries in binary installers

[Antoine Martin]

The MS Windows and MacOS installers contain exploded OpenGL libraries, even after trimming them that's ~2700 files, which is more than half the total. (~4700)
This makes installing / copying the installer files longer than it could be.

[Antoine Martin]

Done for win32 in r20685, r20686 also trims some source files we shouldn't be shipping and some more modules, now down to ~1800. And a lot faster to (un)install.

And we can still zip up some more - but this will require manual testing, some modules don't like loading from zip files, usually if they have data files bundled in with the bytecode.

[Antoine Martin]

• r20687: trim win32 builds further, down to ~1500 files, 385 of which come from xpra
• r20688 (+r20689 fixup): enable site-packages.zip on macos, include OpenGL in it, now down to ~2500 files (mostly in numpy and xpra). We include the source files on macos (and maybe we shouldn't?) which explains some of the extra weight.

This is probably good enough for this release.

[Antoine Martin]

Trim numpy a little bit more:

• r20981 for win32
• r20982 for macos

This will do for now, beta builds posted.

We could trim things more but packaging would become even more brittle, and it might make things harder to test during development.

[Antoine Martin]

Follow up: #2468