configure: Fix silly typo in logging command of check_struct()
configure: Add sanitize_var_name convenience function

This is useful in all the places where special characters in
variable names are manually translated to underscores.
configure: Add check_builtin convenience function
configure: Use check_builtin() where appropriate
hwaccel: consistent name prefixes for start_frame/end_frame/decode_slice

Some hwaccels use name prefixes, some do not, others only use them for
some codecs.  Add prefixes everywhere for consistency.
h264: check for luma and chroma bit dept being equal

The decoder assumes a single bit depth for all the planes
while the specification allows different bit depths for luma
and chroma.

Avoid the possible problems described in CVE-2013-2277

CC: libav-stable@libav.org
vorbisdec: check memory allocations
shorten: set invalid channels count to 0

Prevent the loop shorten_decode_close from writing and freeing out of
the array boundary.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
shorten: K&R formatting cosmetics
shorten: report meaningful errors
shorten: use the unsigned type where needed

get_uint returns an unsigned value, use an unsigned to store
blocksize to make sure the comparison logic is correct and report
correctly the error for the channel count not supported.
dynamic loading of shared faac library
no Werror on implicit-function-declaration and missing-prototypes
custom icon and windows resource
use upstream version tag, my repo is always rebased