Doesn't compile against libexiv2 >= 0.19

[Olivier Tilloy]

(issue originally reported by Rob Healey and Luka Renko)

pyexiv2 (both the latest release, 0.1.3, and the 0.2 development branch) doesn't compile against libexiv2 0.19.
Here is the error message one gets when trying to compile the 0.2 branch against libexiv2 >= 0.19:

osomon@granuja:~/dev/pyexiv2-branches/pyexiv2-0.2$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
g++ -o build/exiv2wrapper.os -c -fPIC -I/usr/include/python2.6 src/exiv2wrapper.cpp
src/exiv2wrapper.cpp: In member function 'void exiv2wrapper::Image::setIptcTagValues(std::string, boost::python::list)':
src/exiv2wrapper.cpp:248: error: 'Exiv2::FindMetadatumById' has not been declared
src/exiv2wrapper.cpp:268: error: 'Exiv2::FindMetadatumById' has not been declared
src/exiv2wrapper.cpp: In member function 'void exiv2wrapper::Image::deleteIptcTag(std::string)':
src/exiv2wrapper.cpp:289: error: 'Exiv2::FindMetadatumById' has not been declared
scons: *** [build/exiv2wrapper.os] Error 1
scons: building terminated because of errors.

[Olivier Tilloy (osomon)]

Exiv2::FindMetadatumById::FindMetadatumById was renamed to FindIptcdatum and moved from iptc.hpp to iptc.cpp in revision 1727. See http://dev.exiv2.org/issues/show/581. A quick fix consists in copying the code for this class in pyexiv2's sources since it's not publicly exported in libexiv2 any longer.

[Olivier Tilloy (osomon)]

Fix committed in the 0.2 branch and backported in the 0.1 branch.
The code for the FindIptcdatum class was copied in pyexiv2's sources.