gstreamer & gst-plugins: --HEAD

Building from gstreamer master is required for development
purpose.

Also gest-plugins-* and gst-libav get --HEAD.

Closes #21665.

Signed-off-by: Samuel John <github@SamuelJohn.de>
gobject-introspection: depends_on :python

To avoid ImportError: Symbol not found: _PyList_Check
during build.
gst-plugins-base: --with-gobject-introspection

should propagate to gstreamer otherwise build will fail.
xmto: fix missing DTD/entities errors

`xmlto` forces the `--nonet` flag on `xsltproc`, which means it throws up an
I/O error whenever it needs to hit the network to pull down any files. So we
patch out the forced flag, and additionally add `docbook-xsl` as a dependency,
which'll reduce the odds of having to hit the network in the first place.

Fixes #21040.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
kytea 0.4.6

Closes #22089.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
zsh completion for brew reinstall

Closes #22061.

Signed-off-by: Samuel John <github@SamuelJohn.de>
Always pass -headerpad_max_install_names to the linker

We use install_name_tool pretty liberally, so we need to take steps to
ensure libraries and executables are always linked with this flag.

Closes #20233.
Fixes #17984.
Fixes #22078.
youtube-dl 2013.08.22

Removed the mirror: the tar from GitHub doesn't have the same checksum

Closes #22095.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
elixir: fixed detection of homebrew installed erlang

Closes #22094.
Closes #22040.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
openssl: run "make depend" to recompute header dependencies

Fixes #21895.
PythonInstalled: Unset PYTHONPATH for `satisfied?`

When a formula `depends_on :python` *and* `depends_on :python3`
the `modify_build_environment` method sets the PYTHONPATH
and the Python 3.x requirement then fails because it finds
the sitecustomize.py from Python 2.x in the PYTHONPATH.