pacman/query.c : -Qo optimization.

I didn't understand why realpath was called on every files of every filelist
in query_fileowner :
ppath = resolve_path(path);

It turns out this is needed for the diverted files. For example, cddb_get
installs /usr/lib/perl5/site_perl/5.8.8/CDDB_get.pm which actually ends in
/usr/lib/perl5/site_perl/current/CDDB_get.pm .

And for making pacman -Qo /usr/lib/perl5/site_perl/current/CDDB_get.pm ,
realpath has to be called on both the target, and the file in the filelist.

However, realpath is costly, and calling it on every single file resulted
in a poor -Qo performance. Worst case :
pacman -Qo /lib/libz.so.1  0.35s user 1.51s system 99% cpu 1.864 total

So I did a little optimization to avoid calling realpath as much as
possible: first compare the basename of each file.

Result:
src/pacman/pacman -Qo /lib/libz.so.1  0.24s user 0.05s system 99% cpu 0.298
total

Obviously, the difference will be even bigger at the first run (no fs
cache), though it's quite scary on my system : 1.7s vs 40s previously.

Signed-off-by: Chantry Xavier <shiningxc@gmail.com>
Signed-off-by: Dan McGee <dan@archlinux.org>

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