Reorder structure elements to make structures smaller and faster on 64 bit systems
This is a first step in cleaning up the client include files (but should be enough to allow us to do future fixes without breaking the library)
This change is part of WL#2872,  Make client library extensible.


configure.in:
  Increased shared library version of client library
  Detect gethrtime (for future)
include/mysql.h:
  Add 'extension' field to all structures to make them extensible
  Reorder structure elements to make structures smaller and faster on 64 bit systems
  Removed an old define that is not needed for MySQL 5.1
include/mysql_com.h:
  Add 'extension' field to all structures to make them extensible
  Reorder structure elements to make structures smaller and faster on 64 bit systems