Perl / C max_chunk_size default sizes

Perl / C max_chunk_size default sizes

default max bundle size == 25K
default max chunk size  == 50K

* note with Ejabberd using 65536 as the default max stanza size, these
  new opensrf defaults mean that all messages will fit the default
  message size constraints -- i.e. no more need to raise the
  max_stanza_size.

Signed-off-by: Bill Erickson <berick@esilibrary.com>