package/vlc: configure.ac does not support --en/--disable-freerdp

package/vlc: configure.ac does not support --en/--disable-freerdp

Vlc configure does not allow disabling the optional dependency to
freerdp:
http://git.videolan.org/?p=vlc/vlc-2.2.git;a=blob;f=configure.ac;h=e021546e284d7daefdb4d94f430eb0bc57722210;hb=HEAD#l1890

Vlc configure prints a warning that the option --disable-libfreerdp
is not used:

configure: WARNING: unrecognized options: --disable-gtk-doc,
 --disable-gtk-doc-html, --disable-doc, --disable-docs,
 --disable-documentation, --with-xmlto, --with-fop, --enable-ipv6,
 --disable-libfreerdp

This can be seen for example in autobuilder logs:
http://autobuild.buildroot.net/results/1a7/1a7893c13f6144e0ecd9f37f2f047c596ccedd35/build-end.log

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>