Steam: first attempt at adding the beta client.

The script installed with this expression only copies a boostrapper and another
script to the user's home folder. Those also need to be patched to get on with
the installation.
Steam: add patch for user stuff and lib paths to wrapProgram.

The binaries that get copied to $HOME need patchelf to run, and after that I
need all the runtime libs in the library path. Still not working as I need
glibc2.15.
steam: add glibc215 to the wrapper.
steam: add all the missing dependancies.

Calling their steam script still segfaults, but I managed to run it from the
shell with all these deps in the lib path.
steam: bypass valve's bootstrapper.

Since there is no way to modify either steam.sh or the steam binary as they are
hash checked, I took the approach of bypassing steam.sh and create a script
that does its job.

For now it segfaults, but when I try to run under strace, it works perfectly.
Need to check this.
steam: update to 1.0.0.18.

I forgot in the previous commit to update the version as I had changed the
tarball hash.

I also modified a bit the launcher script, since xz should only be needed by
the installer.
steam: workaround segfault at startup.

I don't know why, if I call ld-linux.so.2 to launch the game, it segfaults, so
I renamed it to ld.so.
steam: add mesa to library path.

Mesa is needed for Superbrothers: S&S EP, which links to libGLU.
steam: update to 1.0.0.21.

I also updated the patches for the bootsrapper script and fixed a typo, but
didn't test anything.
steam: update to 1.0.0.27

It needed some more sed'ing and more deps. It's still not working as I seem to
need libXdmcp which is not in nixpkgs.
steam: add libXdmcp to dependencies.

I must have been blind. libXdmcp is in nixpkgs, contrary to what I said.
steam: create proper symlinks in $HOME/.steam
Add libtxc_dxtn-1.0.1.

I thought this was needed by Steam, but it only applies when not using
propietary drivers, and even then it doesn't look like well supported.
steam: create some missing symlinks in the script.

In the original script it says they are temporary, but without those simlinks
Osmos and others fail to start with SteamAPI_Init() failed.
steam: update to 1.0.0.28
steam: add amd64 version and point url to fix version (as suggested by aristid).

Valve has a repository with fixed version packages, so use that instead of the
steam.deb I was using. They also have amd64 packages there.
steam: revert adding amd64 version.

It turns out that the .deb only contains the changelog and some other docs.
Revert back to using the i686 version, but keep the double url for the future.
steam: add flashplayer plugin support.

The videos work, but there is a problem with sound:
ALSA lib dlmisc.c:236:(snd1_dlobj_cache_get) Cannot open shared library
/nix/store/9z51hr9l19vdhgmqd60jwwrg6ny5md2d-alsa-plugins-1.0.26/lib/alsa-lib/libasound_module_pcm_pulse.so

It tries to open a 64bit plugin, which obviously fails. I think this depends on
/etc/asound.conf, but I'm not sure how to fix it.

Regardless of the problem, in one computer I tried the sound works but other
apps cannot output sound. In another, the sound doesn't work and other apps
continue working as normal.
Steam: fix and update to 1.0.0.39