Tunneling support is gone upstream, so drop the patch and add
Config.in.legacy handling for the option.

Celt051 is no longer a hard dependency, and opus is a new optional
dependency, so adjust the dependencies to match.

Python / pyparsing are not needed as the tarball contains the generated
files (this should presumably have been host-python in the first place as
these are used at build time), but we need a small workaround to convince
configure that they really aren't needed.

Alsa-lib is only needed for client support, and the configure script checks
for X11/Xext/Xrender, so adjust the dependencies to match.

A user manual is now generated by default if asciidoc is available, so
explicitly disable that.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>