This will bring our doxyfile closer to the modern world and clean up some warnings in the doxygen output during a regular build. I believe it is pretty fair to use 1.7.6.1 given it released in 2011, with the 1.7.x branch a year prior. The current branch is 1.8, which released 2012, but I believe 1.7.6.1 is sufficient.
Updated by running doxygen -u doc/Doxygen.in with Doxygen 1.7.6.1. The only manual change was adding 'Free Lossless Audio Codec' to PROJECT_BRIEF.
When building outside of the source tree, the Doxyfile needs to be
generated in the build tree and should point to the proper paths for
include directories and html footer.
The generated api files to install should also be taken from the build
tree instead of the source tree.
Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>
