Add missing .gitignore entries and clean rules

ticket: 7585
Add krb5_free_enctypes API

Rename krb5_free_ktypes to krb5_free_enctypes and add it to the public
API.

ticket: 7584
Fix a memory leak in krb5_get_init_creds_keytab

lookup_etypes_for_keytab was not freeing the keytab entries it
iterated over.  Reported by nalin@redhat.com.

ticket: 7586
target_version: 1.11.2
tags: pullup
Simplify and clarify lookup_etypes_for_keytab
Fix dependencies in tests/gssapi

Use $(COMMON_DEPS) instead of $(COMMON_DEPLIBS) for dependencies; the
latter appears to be a typo.  Fixes build when using "make -j".

ticket: 7587 (new)
target_version: 1.11.2
tags: pullup