LU-6349 idl: add PTLRPC definitions to enum

LU-6349 idl: add PTLRPC definitions to enum

Add PTLRPC definitions to enums for cleanliness, and use them:

    enum lustre_msg_version for LUSTRE_*_VERSION
    enum lustre_msg_magic for LUSTRE_MSG_MAGIC_*
    enum lustre_msghdr for MSGHDR_*

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Ie17619bfc2433339ab32e257d596adf64c2c4ff0
Reviewed-on: https://review.whamcloud.com/30958
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>