exiv2 soname bump

[Rex Dieter]

exiv2-0.21 was released recently, and includes a soname bump.  I plan on
importing this into rawhide next week sometime, if all goes well.

Here's a scratch build for testing,
http://koji.fedoraproject.org/koji/taskinfo?taskID=2636872

I've done a few test builds of the items below, and the only one that
ftbfs is pyexiv2 (a usual suspect, being a low-level binding).

and a list of affected pkgs,
$ repoquery --repoid=rawhide-source --archlist=src \
  --whatrequires exiv2-devel | sort
darktable-0:0.7-1.fc15.src
geeqie-0:1.0-4.fc14.src
gipfel-0:0.3.2-5.fc15.src
gnome-color-manager-0:2.91.2-1.fc15.src
gnome-commander-3:1.2.8.8-3.fc15.1.src
gpscorrelate-0:1.6.1-2.fc14.src
gthumb-0:2.12.1-1.fc15.src
hugin-0:2010.2.0-1.fc15.src
immix-0:1.3.2-9.fc14.src
kdebase-runtime-0:4.5.80-3.fc15.src
kdegraphics-7:4.5.80-2.fc15.src
kipi-plugins-0:1.6.0-1.fc15.src
koffice-3:2.2.84-2.fc15.src
kphotoalbum-0:4.1.1-7.fc15.src
krename-0:4.0.5-1.fc15.src
libextractor-0:0.6.2-1503.fc15.src
libgexiv2-0:0.2.0-1.fc15.src
merkaartor-0:0.16.3-1.fc15.src
pyexiv2-0:0.2.2-2.fc15.src
qtpfsgui-0:1.9.3-5.fc14.src
rawstudio-0:1.2-6.fc15.20100907svn3521.src
strigi-0:0.7.2-6.fc15.src
ufraw-0:0.17-1.fc14.src