doc: build: Reduce size of doxygen.cfg and doxygen build o/p

doxygen.cfg only needs to contain non-default options.
Removing other options shaves 4KB (off a 5KB file).
Also remove options that are obsolete at the latest doxygen release:
 PERL_PATH, MSCGEN_PATH and PAPER_TYPE=a4wide (defaults to a4).

While being about it, send doxygen stdout to /dev/null to make (future)
warnings easier to see.

Signed-off-by: Duncan Roe <duncan_roe@optusnet.com.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

0 files changed, 0 insertions, 0 deletions