Add 'doc' target to create doxygen documentation (ATLINFR-1843)
Add support for a doc
target to atlas_project
if the DOXYGEN
option is
specified. In that case a copy of the given doxyfile is made in the build
area and the doxygen INPUT is set to the list of selected packages. The
doxygen output is stored in the 'docs' directory of the build area. No
changes are made to the source area.