Original commit message from CVS:
Added checking for all the tools used to make documentation.
If documentation cannot be generated, whatever is available will still be
installed.
videosink/imagetest is now a check_PROGRAM
Original commit message from CVS:
Fix another bug in make install for fwg (complained becuase there were no
pngs to install).
I should have got up more slowly today...
Original commit message from CVS:
Added framework for writing filter writers guide.
Extracted much of the makefile from docs/manual into a shared file which
is included, so it can be re-used.
