Make libjafs buildable again

Make libjafs buildable again

libjafs is surprisingly close to being buildable. Fix a few misc
things which have bitrotted over the years so it is possible to
actually build:

 - Add -I$SRC/config to the cflags, so we can include afsconfig.h

 - Remove references to the nonexistant rxkstats.o

 - Do not link with UAFS' AFS_component_version_number.o, since this
   gives us duplicate version number symbols

 - Include afs_vosAdmin.h in Group.c, to satisfy some missing symbols

Change-Id: Ie8da88872288073d080a58ed7fe8c8b52052488e
Reviewed-on: http://gerrit.openafs.org/6524
Reviewed-by: Steven Jenkins <steven@synaptian.com>
Tested-by: Steven Jenkins <steven@synaptian.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>