Minimize hash key creation overhead by directly applying MD5 instead of  copying / duplicating the key. Also, check for NULL keys directly on the interface.
Minimize hash key creation overhead by directly applying MD5 instead of 
copying / duplicating the key. Also, check for NULL keys directly on the interface.

* subversion/libsvn_subr/cache-membuffer.c
  (get_group_index): don't calculate the 16 byte hash; require it to come in
  (membuffer_cache_set, membuffer_cache_get,
   membuffer_cache_get_partial, membuffer_cache_set_partial):
   adapt callers; invalid groups are impossible now
  (svn_membuffer_cache_t): ensure proper alignment for prefix;
   add temp buffer for combined key
  (combine_key): calculate & combine hashes
  (svn_membuffer_cache_get, svn_membuffer_cache_set,
   svn_membuffer_cache_get_partial, svn_membuffer_cache_set_partial):
   adapt callers; handle NULL keys

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