Pointed-out-by: Rafael Carré.

This allow a little bit more flexibility and won't require the same level of code quality in configure tests (is that a plus?).

Warnings that are 'safe' to be treated as error should be added here as well.

I hope this will raise VLC code quality, and tend to lower the hudge number of warnings. Some of them are sometimes letal but hidden by others.

And bumping autoconf version seems to be a bit much for such a small improvement

Configure: update macro to deal with the case where you want --enable-foo, but the module name is not foo.

So, add a new argument that can be empty
This happens for --enable-dv (access_dv) --enable-shout (stream_output_shout)

--enable-foo will search for the foo.pc and die if not provided
--disable-foo will not search anything related to foo
'' will search for foo.pc and give a message if foo.pc is not provided.

Commit changes to m4/private.m4. Please yell (and remove the file from git) if this wasn't supposed to be committed.

As an alternative, we could avoid shipping all the gettext macros and
require developpers have gettext if they want to rebuild ./configure
from a source tarball. I'd tend to lean for this option.

The whole point of keeping the m4 and po/Makefile.in.in is to not need
to have the same version all over the place anyway, otherwise we might
as well put all these files to .gitignore...

Remove some old m4 macros as well.

and fix the M4 ignore rules

This reverts commit 8b71b104.
Most developers did not update their gettext install
Bumping gettext requirement is useless.

Adds libgcrypt.m4 for systems running autotools without libgcrypt-dev installed
Prefers tabs over spaces in Makefiles

vlc-config: fixed optimizations by splitting CFLAGS_OPTIM into CFLAGS_OPTIM_SIZE and CFLAGS_OPTIM_SPEED, and only one of which is used depending on value --enable-optimize-memory, moreover CFLAGS_NOOPTIM is set to -O0 rather than -O2 whenever possible