Bugfix: Since at least one of unix (or __APPLE__) or WIN32 is required by util.h, make sure unix is defined if WIN32 is not

Neither were being defined by default for GCC -std=c1x

compat.h

@@ -18,6 +18,10 @@
 
 #include <stdbool.h>
 
+#if !(defined(WIN32) || defined(unix))
+#define unix
+#endif
+
 #ifdef WIN32
 #include <errno.h>
 #include <time.h>