Fixing out-of-tree failures in hw/dmx/doc

[Cyril Brulebois]

Hi,

I saw Dan's reply, but I'm posting anyway the tiny patch series that
fixes the out-of-tree build for me (with devel docs enabled, with
doxygen; not tried distcheck).

[PATCH 1/3] hw/dmx/doc: Fix missing slash in css target.
  Trivial enough.

[PATCH 2/3] hw/dmx/doc: Specify {src,build}dir in DOXYGEN_SRC.
  Distinguish between source and build directories.

[PATCH 3/3] hw/dmx/doc: Move from $(builddir) to $(abs_builddir).
  http://www.gnu.org/software/hello/manual/autoconf/Preset-Output-Variables.html
  says builddir is equal to '.'; I tried riping out $(builddir)/
  entirely, but that didn't help. That's why I went for $(abs_builddir).

As for the tested automake versions (both work with the 3 patches, both
fail without the 3rd one):
  automake (GNU automake) 1.11.1 (the default for me)
  automake (GNU automake) 1.10.3

KiBi.