Ticket History #6954: Add new cache collection APIs

* krb5_cc_get_full_name retrieves the full type:name of a cache.
* krb5_cc_switch makes a cache the primary cache.
* krb5_cc_cache_match searches the collection for a client principal.
* krb5_free_string releases a string (for the krb5_cc_get_full_name
result).

All of these are from Heimdal except for krb5_free_string (Heimdal uses
krb5_xfree).

https://github.com/krb5/krb5/commit/f784a37909b68b7dfc1eed8c3a0e014639c90e45
Commit By: ghudson
Revision: 25155
Changed Files:
U trunk/src/include/k5-int.h
U trunk/src/include/krb5/krb5.hin
U trunk/src/lib/krb5/ccache/cc_dir.c
U trunk/src/lib/krb5/ccache/cc_file.c
U trunk/src/lib/krb5/ccache/cc_keyring.c
U trunk/src/lib/krb5/ccache/cc_memory.c
U trunk/src/lib/krb5/ccache/cc_mslsa.c
U trunk/src/lib/krb5/ccache/ccbase.c
U trunk/src/lib/krb5/ccache/cccursor.c
U trunk/src/lib/krb5/ccache/ccfns.c
U trunk/src/lib/krb5/krb/kfree.c
U trunk/src/lib/krb5/libkrb5.exports
U trunk/src/lib/krb5_32.def