Various build fixes

Hi,

Here are a couple of patches fixing problems I have had with the build
system.

wxwidgets_gtk_fix.diff commes from the upstream CVS and fixes a compile
error when using a recent version of GTK+

redland.diff fixes several issues. It follows the advice from redland
author to include <redland.h> instead of <librdf.h>. If avoids the build
to fail if the libraptor development files are present. It fixes errors
when using the --enable-system-redland flag.

In addition, add_destdir_to_Makefile.diff allows the use of the DESTDIR
variable when calling `make install`. This is commonly used by other
projects (via automake) and is useful when building packages.

I would recommend you include the first two patches, the third one is only
a suggestion.

If you have any further question about these patches, please don't
hesitate to contact me.

HTH

Regis
-- 
"While a monkey can be a manager, it takes a human to be an engineer" Erik
Zapletal