return special_hitpoints to using a specific value instead of a multiplier;
this was extensively tested in both single-player and multiplayer, using change-ship-class and changing ship loadout, against ships both higher and lower in hitpoints, to ensure it didn't re-break Mantis #2326

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9502 387891d4-d844-0410-90c0-e4c51a9137d3
onlyjob's spelling fixes, per Mantis #2777

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9503 387891d4-d844-0410-90c0-e4c51a9137d3