Also don't reset memory after it's allocated if we do that with
calloc.

- Add a configure test for the attribute, during xine build process.
- Define the attribute as supported when using GCC 2.95 or later
  outside xine build process.
- Use the new XINE_PACKED define instead of the attribute directly.
- Check for SUPPORT_ATTRIBUTE_PACKED rather than doing strange
  subdefines.

The xine_xmalloc() function is going to be deprecated, as its
behaviour is rarely needed as such, and it's thus misused.

With this, almost all uses of xine_xmalloc() with static size (for
instance the value returned by sizeof()) or with a size that is
guaranteed not to be zero (like strlen()+1) are replaced with calls to
either calloc(1, ...) or malloc().

malloc() is used whenever the allocated memory is going to be
immediately overwritten, while calloc() is used in every other case,
as it sets the whole memory area to zero.

--HG--
extra : transplant_source : %8F%98%EC%02%1E%83%F0s%06X%83C%205Y%80%B12%CC%E1

Occasionally when playing h264-encoded files, green blocks will appear
at the edges of the frame, and get smeared around (following the motion
vectors, of course).  This bug has existing in Xine for well over a
year, and I keep hoping it will be fixed, but it never was.

I recently learned that gstreamer had a similar problem and it was fixed
last year.  With this as a hint, I found
http://bugzilla.gnome.org/show_bug.cgi?id=364139 and the patch attached
to that bug.

I've adapted that patch to xine, and it is attached.  I have compared
clips before and after applying this patch, and in all cases the green
artifacts have gone away, and I have seen no negative side effects.