Fix a commit-editor bug spotted by Gustav Munkby.
Fix a commit-editor bug spotted by Gustav Munkby.

Gustav was driving an RA commit editor directly from his C program,
and passed an invalid base-rev into open_file().  He instantly got an
out-of-date error, doh.

* libsvn_repos/commit.c (open_file): don't do an early out-of-dateness
  check on an invalid revnum.  We shouldn't be comparing -1 to anything.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion