log4cpp: disable documentation build and install

log4cpp: disable documentation build and install

We don't need the documentation on target.

Also fixes:
http://autobuild.buildroot.net/results/402/402587fe3ba9d537195ba470cf6f19f25ac246bf/
http://autobuild.buildroot.net/results/ea2/ea257496f51665b0a6b03f31e50744761c5d43da/
http://autobuild.buildroot.net/results/353/3533a32a7de7dae288558f43eb2b068081939e4d/

and many more.

Cc: Damien Lanson <damien@kal-host.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>