Clean up language nits in HACKING.
Clean up language nits in HACKING.

Patch by: Chris Pepper <pepper@reppep.com>

* HACKING:
  s/commit-access/commit access/
  s/code base/code/
  Include missing trailing slash on http://apr.apache.org (slashes are used
  sometimes and skipped sometimes, but they *are* part of the real URL).
  Clarify that the key for secure programming is developer understanding,
  not necessarily further education.
  Re-word 'staked ownership', as it was a sloppy idiom.
  Additional linguistic tweaks.

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