Make branch for md5 collision protection changes.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.7.x-md5-collision@1600982 13f79535-47bb-0310-9956-ffa450edef68
On the 1.7.x-md5-collision branch: Merge r1550691, r1550772, r1600909 from trunk.

svn_hash_gets(...) was changed to apr_hash_get(..., APR_HASH_KEY_STRING) since
the svn_hash_gets() macro was not available in 1.7.x.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.7.x-md5-collision@1600983 13f79535-47bb-0310-9956-ffa450edef68
Merge the 1.7.x-md5-collision branch:

 * r1550691, r1550772, r1600909
   Guard against MD5 hash collisions when finding cached credentials.
   Justification:
     MD5 collision attacks exist and could be used to trick a client into
     sending cached credentials to a server other than what they were
     cached for.
   Notes:
     Branch is required due to svn_hash_gets() not being available in 1.7.x
   Branch:
     ^/subversion/branches/1.7.x-md5-collision
   Votes:
     +1: breser, stefan2, philip


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.7.x@1615193 13f79535-47bb-0310-9956-ffa450edef68