Ticket History #6957: Add krb5_cc_select() API and pluggable interface

The interface has two built-in modules. The realm module guesses a
cache based on the server realm if it is known. The k5identity module
(Unix only) chooses a client principal based on rules in a .k5identity
file in the user's homedir.

https://github.com/krb5/krb5/commit/02536734d9443f62b75c3df97b4079fbe3d3e6cf
Commit By: ghudson
Revision: 25158
Changed Files:
U trunk/src/gen-manpages/Makefile.in
A trunk/src/gen-manpages/dot.k5identity.M
A trunk/src/gen-manpages/k5identity.M
U trunk/src/include/k5-int.h
U trunk/src/include/k5-trace.h
A trunk/src/include/krb5/ccselect_plugin.h
U trunk/src/include/krb5/krb5.hin
U trunk/src/lib/krb5/ccache/Makefile.in
U trunk/src/lib/krb5/ccache/cc-int.h
A trunk/src/lib/krb5/ccache/ccselect.c
A trunk/src/lib/krb5/ccache/ccselect_k5identity.c
A trunk/src/lib/krb5/ccache/ccselect_realm.c
U trunk/src/lib/krb5/ccache/deps
U trunk/src/lib/krb5/krb/init_ctx.c
U trunk/src/lib/krb5/krb/int-proto.h
U trunk/src/lib/krb5/libkrb5.exports
U trunk/src/lib/krb5_32.def