imlib2: bump to version 1.4.6

Also add two upstream patch to fix a warning and a build failure of the
version 1.4.6.

Also add AUTORECONF because one patch change the file
"src/lib/Makefile.am".

Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>