Update subversion package to 1.6.16.

Security fix seems to related to www/ap2-subversion.

Version 1.6.16
(02 Mar 2011, from /branches/1.6.x)
http://svn.apache.org/repos/asf/subversion/tags/1.6.16

  User-visible changes:
  * more improvement to the 'blame -g' memory leak from 1.6.15 (r1041438)
  * avoid a crash in mod_dav_svn when using locks (r1071239, -307)
            See CVE-2011-0715, and descriptive advisory at
            http://subversion.apache.org/security/CVE-2011-0715-advisory.txt
  * avoid unnecessary globbing for performance (r1068988)
  * don't add tree conflicts when one already exists (issue #3486)
  * fix potential crash when requesting mergeinfo (r902467)
  * don't attempt to resolve prop conflicts in 'merge --dry-run' (r880146)
  * more fixes for issue #3270.

  Developer-visible changes:
  * ensure report_info_t is properly initialized by ra_serf (r1058722)
  * locate errors properly on a malfunction (r1053208)
  * fix output param timing of svn_fs_commit_txn() on fsfs (r1051751)
  * for svn_fs_commit_txn(), set invalid rev on failed commit (r1051632, -8)
  * fix sporadic Ruby bindings test failures (r1038792)
  * fix JavaHL JVM object leak when dumping large revisions (r947006)
  * use Perl to resolve symlinks when building swig-pl (r1039040)
  * allow Perl bindings to build within a symlinked working copy (r1036534)
  * don't overwrite the LD_LIBRARY_PATH during make check-swig-pl (r946355)
  * improve unit tests for some fs functions (r1051744, -5, -3185, -241)

(taca)