Instead of passing "subversion" to sasl_server_init and "svn" to

Instead of passing "subversion" to sasl_server_init and "svn" to
sasl_client_new sasl_server_new, define new macro for "svn" and
use that everywhere.  Reduces burden on administrators, having to
configure /usr/lib/sasl2/subversion.conf on the one hand but using
svn on the other hand (e.g. in making a Kerberos principal).

* subversion/include/private/ra_svn_sasl.h
  (SVN_RA_SVN_SASL_NAME): Add new macro.

* subversion/libsvn_ra_svn/cyrus_auth.c
  (new_sasl_ctx): Use SVN_RA_SVN_SASL_NAME instead of "svn".

* subversion/svnserve/cyrus_auth.c
  (initialize): Use SVN_RA_SVN_SASL_NAME instead of "subversion".
  (cyrus_auth_request): Use SVN_RA_SVN_SASL_NAME instead of "svn".

* notes/sasl.txt
  Update.

git-svn-id: http://svn.collab.net/repos/svn/trunk@29242 612f8ebc-c883-4be0-9ee0-a4e9ef946e3a