Change instruction size calculation to report unsigned values.

include/zipr_plugin.h

@@ -41,7 +41,7 @@ class ZiprPluginInterface_t
 		{
 			return false;
 		}
-		virtual int WorstCaseInsnSize(libIRDB::Instruction_t*, Zipr_t *)
+		virtual size_t WorstCaseInsnSize(libIRDB::Instruction_t*, Zipr_t *)
 		{
 			return 0;
 		}