On the invoke-diff-cmd branch: Tidy and improve code, comment out faulty code.

* subversion/libsvn_client/diff.c 

  (svn_io_create_custom_diff_cmd): Add base condition check for
  'found' variable.  Tidy code (spaces and indentation).  Fix pcalloc
  issue.  Resize ret allocation. 

* subversion/svn/log-cmd.c

  (display-diff): Comment out --invoke-diff-cmd and replace with NULL,
  temporary measure to ensure svn compiles.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/invoke-diff-cmd-feature@1484986 13f79535-47bb-0310-9956-ffa450edef68