In some build environments, dependencies on libkrb5support can be
generated just from static inline functions in our header files, even
if those functions aren't used. In two test plugin modules, use
$(KRB5_BASE_DEPLIBS) and $(KRB5_BASE_LIBS) to depend on libkrb5support
as well as libkrb5. (This also pulls in libk5crypto, which is
unnecessary for these modules, but is inconsequential for a test
module.) Reported by Will Fiveash.