osx requires ssize_t

dtool/src/parser-inc/stdtypedefs.h

@@ -25,6 +25,7 @@
 #define STDTYPEDEFS_H
 #ifndef __APPLE__
 typedef unsigned int size_t;
+typedef int ssize_t;
 typedef int off_t;
 typedef unsigned int time_t;
 typedef int clock_t;