Log some errors instead of ignoring them.
Log some errors instead of ignoring them.

* subversion/mod_dav_svn/liveprops.c
  (insert_prop_internal):
    Log an APLOG_ERROR-level error whenever ###error### is dumped into the
    data stream in lieu of an actual value.
  
The log entries look like this:
[Mon Jan 30 17:26:11 2012] [error] [client ::1] (160017)APR does not understand this error code: Can't get fetch or compute md5 checksum of '/A': traced call
where #160017 is the svn_error_t.apr_err code (for which-error.py)

The 'traced call' is due to the direct use of serr->message.  It's used this
way throughout mod_dav_svn, so I'm following suit in this commit.

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