samba: revert to 3.6.8

samba 4.0.0+ doesn't reliably compile on Snow Leopard. In
addition, the autoconf build used by our 4.0.0 formula only
installs a subset of samba's tools. (See the readme for details.)
See #17820.

Once these issues are resolved, we can upgrade to 4.0.3.

This reverts commit 2229c7d9bb04bb523c9d103c5d8f2e9a60098ee5.
android-sdk r21.1

Closes #17851.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
opam-0.9.3

Closes #17863.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
ccache 3.1.9

Closes #17857.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
BaseX 7.6

Closes #17855.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
gearman 1.1.5

Closes #17791.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
node 0.8.20

Closes #17869.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
libpng: use archive URL
libxmp 4.0.0
xmp 4.0.0