Extend UCS normalization checks in 'svnadmin verify' to mergeinfo.

* subversion/include/svn_repos.h (svn_repos_notify_warning_t):
   New constants 'svn_repos_notify_warning_denormalized_mergeinfo'
   and 'svn_repos_notify_warning_mergeinfo_collision'.
  (svn_repos_verify_fs3) Update documentation of parameter 'check_ucs_norm'.
* subversion/libsvn_repos/dump.c (dump_node): Check UCS normalization
   of paths in added or changed svn:mergeinfo property values.
  (check_name_collision): Fix latent bug: copy the normalized name
   from the membuf into the pool, so that the hash key doesn't change
   during the iteration.
* subversion/svnadmin/svnadmin.c (options_table): Update the documentation
   of the --check-ucs-normalization option.

* subversion/tests/cmdline/svnadmin_tests.py (verify_denormalized_names):
   Update expected results.
* subversion/tests/cmdline/svnadmin_tests_data/normalization_check.dump:
   Add svn:mergeinfo properties for UCS normalizaiton checks.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1545081 13f79535-47bb-0310-9956-ffa450edef68