forward of [89044739]

I removed:
 i_x/i_y: redondant with region i_x/i_y. Now a subpicture always represent the
 whole video.
 i_flags: unused anywhere in the core.

 I may have broken a few video filters (osdmenu mainly). I will fix it if you
report the problem and the way to reproduce it.

Fix unitialized pointer usages (possibly exploitable).

There is no functional changes.

Conflicts:

	NEWS

Fortunately, var_DelCallback does the job properly already.

libvlc kills the interfaces when it dies anyway.

It merely wrappeded the SAP object.

(cherry picked from commit 77cc89e3d9349f3d5a2de947f9be478dd28436dd)
(cherry picked from commit 6d4830b864af38d7126aee103a6bcfe76bc80e89)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

when --enable-v4l2 was passed to configure, alsa was searched and linked
against if found (only do that when alsa wasn't disabled)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

when --enable-freetype was passed to configure, fontconfig was searched
and linked against if found (provide --enable-fontconfig which is
default)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>