Cleanup includes.
Remove workaround for GCC 4.7 which is not supported any more.
Use correct WKB byte order marker.

This depends on the byte order of the CPU we are using. Tests against hard
coded byte sequences only work on little endian, so they are #ifdef'd out
otherwise.
Fix memory leak in XML Parser.
Refactor over-complex XML Parser code using a new ExpatXMLParser class.
Further refactoring of XMLParser class.
Improved exception handling in gzip (de)compression, more XML file tests.

The gzip (de)compressor got its own exception class that not only gives back
the error message from the gzip library but also access to underlying error
codes.
The XML file tests were expanded and can now also check gzipped XML files.