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

*** 60,69 ****
--- 60,70 ----
  #include        <sys/types.h>
  #include        <stdlib.h>
  #include        <stdio.h>
  #include        <string.h>
  #include        <assert.h>
+ #include        <unistd.h>
  
  /*
   * Parser flags:
   *
   *      PARSEFIXED