Try to use the int32 and friends on all Unixes -- not just SGI's Irix.
--- include/icc34.h.in.orig	Tue Jul 22 06:10:02 2003
+++ include/icc34.h.in	Sun May 23 11:45:09 2004
@@ -191,8 +191,10 @@
 typedef icUInt32Number   icU16Fixed16Number;
 
 #else
+#ifdef __unix__
 #ifdef __sgi
 #include "sgidefs.h"
+#endif
 
 typedef __int32_t       icSignature;