Explicitly use SRCDIR and BUILDDIR in Doxyfile files to reference input
files. This seems to be a sufficient fix for an issue where the build
would fail when libsigrok/ was located in a directory that was a symlink.
This fixes bug #547.
This is more specific and prevents any potential issues e.g. when
multiple distro packages might ship with a generic file like
sigrok-logo-notext.png that's supposed to be installed in the same place.
The source file enum.hpp was not found when not building in the source
tree. Also, extraction of the brief description did not work correctly
when there was additional XML markup inside the <para> element.
Uwe Hermann
Marcus Comstedt
Martin Ling