Remove external thread for fontdbbuiler, and do it on load. First run is
slower on windows, so show dialog about it to user. Following runs
should be much faster (atleast according to my own tests).

So on optimal case user sees that font-dialog only once when initial
cache is created.

One idea was to load freetype-module on start of vlc, so it would create
that cache on start of vlc instead of start of video (when showing
title), and could be changed to show something like 'VLC is starting
first time, please wait a while...' or so.

Feel free to revert/change/complain about this if it doesn't work for
you.

This partially reverts f1175e71.

This is just pedantic. Nobody links against plugins anyway.

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)

Be careful, while dv was updated to the new APIs, dc1394 wasn't

--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.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>