If Berkeley DB version 2.x is used as a slapd back-end a not-initialized
Datum structure will raise an EINVAL error in (DB)->put().

  This could cause problems on odd systems.  The generic
  headers should be extended as needed to include necessary
  system headers or, if necessary, make explicit declarations.
Extended ac/string.h header to look for string.h/strings.h if
  STDC_HEADERS is not defined.  Also provide basic declarations for
  str*() functions.  This could cause problems on odd systems.
Extended ac/unistd.h header to define basic declaration for misc
  functions that might be missing from headers.   This includes
  externs for getenv(), getopt(), mktemp(), tempname().
Protect fax500.h from multiple inclusion.  Moved includes of
  system/generic headers back to source files.
Made mail500 helper functions static.
Fixed includes of ctype.h, signal.h, etc. to use generics.
lutil/tempname.c: was including stdlib.h twice, one should stdio.h.
Wrapped <sys/resource.h> with HAVE_SYS_RESOURCE_H.
lber/io.c/ber_get_next(): Changed noctets back to signed.
  Used with BerRead which expects signed int as second arg and
  returns signed int.

Most function and variable definitions are now preceded by its extern
definition, for error checking.  Retyped a number of functions, usually
to return void.  Fixed a number of printf format errors.

API changes (in ldap/include):
  Added avl_dup_ok, avl_prefixapply, removed ber_fatten (probably typo
  for ber_flatten), retyped ldap_sort_strcasecmp, grew lutil.h.

A number of `extern' declarations are left (some added by protoize), to
be cleaned away later.  Mostly strdup(), strcasecmp(), mktemp(), optind,
optarg, errno.

Fix pointer truncation to int by including prototypes in forward declarations.

LTHREAD still needs work.