Fix GCC warning: dereferencing type-punned pointer will break strict-aliasing rules.
Fix GCC warning: dereferencing type-punned pointer will break
strict-aliasing rules.

* subversion/libsvn_ra_svn/sasl_auth.c
  (svn_ra_svn__do_auth): Make 'creds' an opaque object, removing the
    need for a cast.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion