Fix compile issue on Linux re: INT_MAX / <limits.h>

git-svn-id: svn://svn.icculus.org/fs2open@10195 387891d4-d844-0410-90c0-e4c51a9137d3
Tweak insignia limits again per Oddgrim's recommendations

http://www.hard-light.net/forums/index.php?topic=86195.msg1722757#msg1722757

git-svn-id: svn://svn.icculus.org/fs2open@10196 387891d4-d844-0410-90c0-e4c51a9137d3