Use XSLT file to open JDiveLog logs

Use XSLT file to open JDiveLog logs

Open JDiveLog files by translating them to subsurface format using XSLT.
These files are identified by the name of the first element (JDiveLog)
and transform is applied to only these.

The XSLT feature is compiled in only if libxslt is installed. The
transformation files are installed globally in Linux under
/usr/share/subsurface/xslt. Windows and OSX still need appropriate Makefile
changes and testing.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>