distcc: deprecate package, only useful for development

Since quite a while, we have deprecated, and then removed the support
to build a compiler on the target. Therefore, having a distcc package
for the package is quite useless, and this patch consequently marks it
as deprecated so it can be removed in a future version of Buildroot.

Fixes:

  http://autobuild.buildroot.net/results/16b/16be2138c8e5ba785fa2ad55b478dcd1b6fb5123/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>