-GNU_REGEX - use with GNU regex(3)
-DES - use to add encryption support (requires crypt(3))
-NO_REALLOC_NULL - use if realloc(3) does not accept a NULL pointer
-BACKWARDS - use for backwards compatibility
+DES - to add encryption support (requires crypt(3))
+NO_REALLOC_NULL - if realloc(3) does not accept a NULL pointer
+BACKWARDS - for backwards compatibility
+NEED_INSQUE - if insque(3) is missing