releasing package apt version 0.9.15.1
fix remaining testcase-bugs from my armel box

Git-Dch: Ignore
simplify code to make compilers happy

Does the same as before, but is a bit simpler on the logic for humans as
well as compilers. scan-build complained about it at least with:
"Result of operation is garbage or undefined"

Reported-By: scan-build
update libapt-pkg.symbols file
bump Standards-Version to 3.9.5 (no changes needed)
disable doxygen undocumented method warning

Very few methods we have are documented, so this is A LOT of noise
hidden the "interesting" warnings about methods which are documented,
but incorrectly and such stuff.

Git-Dch: Ignore
do not use an empty APT_CONFIG environment variable
always cleanup patchfiles at the end of rred call

With APT::Get::List-Cleanup disabled the ed-style patch files are
lingering in the lists/ directory otherwise. That was kinda okay in the
old none-client-merge as the filename was always the same so it was
constantly overridden, but now with different names for client-merge
quiet a few could pill up on the system and are used by the next call
as it picks them up based on the filename.
use VersionSet in download to handle repeats

Closes: 738103
use utimes instead of utimensat/futimens

cppcheck complains about the obsolete utime as it was removed in
POSIX1.2008 and recommends usage of utimensat/futimens instead
as those are in POSIX and so commit 9ce3cfc9 switched to them.
It is just that they aren't as portable as the standard suggests:
At least our kFreeBSD and Hurd ports stumble over it at runtime.
So to make both, the ports and cppcheck happy, we use utimes instead.

Closes: 738567