Fix a bug in svn_uri_is_canonical; it would begin path verification at
the beginning of the host name, and if the host name was "." would think
it found an invalid path segment.

* subversion/libsvn_subr/dirent_uri.c (svn_uri_is_canonical):
   Set the segment pointer to the beginning of the schema data before
   verifying same, otherwise it would point at the beginning of the
   host name.

* subversion/tests/libsvn_subr/dirent_uri-test.c (uri_canonical):
   Add a couple cases that tripped up the buggy svn_uri_is_canonical.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1516806 13f79535-47bb-0310-9956-ffa450edef68