I meant to do this a long time ago, but basically it accounts for the new XP_SOLARIS build flag that never made it into the MailNews code. Additionally, it enables a compatibility flag for Solaris 11.4 that allows us to use the three-argument implementation of ctime_r still used by Solaris 11.3 and illumos (which also appears equivalent to the NSLDAPI_CTIME implementation used by libldap internally). Also, the ctime_r function has been added to the time.h header library for a while now, not sure why Mozilla thought we didn't have a ctime_r implementation.
