UNIX98 requires unistd.h for getopt, and requires -D_XOPEN_SOURCE=500.

@@ -60,10 +60,11 @@
 #include        <sys/types.h>
 #include        <stdlib.h>
 #include        <stdio.h>
 #include        <string.h>
 #include        <assert.h>
+#include        <unistd.h>
 
 /*
  * Parser flags:
  *
  *      PARSEFIXED