Move some library dependencies closer to their use

LIB_AFSDB (aka -lresolv) is only required by auth/cellconfig.c.
Let libtool record that liboafs_auth.la depends on LIB_AFSDB and do
not put it in XLIBS.  We must retain LIB_AFSDB explicitly where we
use the convenience library libauth_pic.la (i.e., libafsauthent and
pam) since the convenience libraries cannot record this dependency
information.

Likewise, LIB_crypt is used only by kauth.

Change-Id: Ia133aadba90b2fc58cf43a9b534560c3a35f2cc2