ea90ca86664c73fb8d415f3cc7baacdf8a6dd685("Move some infra bits of
lib/krb5/ to lib/base/ (2)") forgot to add typedefs
heim_get_instance_func_t
krb5_get_instance_t
required for compilation of krb5_get_instance style plugins.
Change-Id: I3130f86034be1f9f79694eca0d1b309e247fd03f