autoconf test for nsl and socket libraries (ITS#1543)

[china@thewrittenword.com]

Full_Name: Albert Chin-A-Young
Version: 2.0.21
OS: Solaris, HP-UX, IRIX, Tru64 UNIX, AIX
URL: ftp://ftp.thewrittenword.com/outgoing/pub/openldap-2.0.21-2.patch
Submission from: (NULL) (64.32.187.114)


It is generally considered bad to use a library simply if it exists. This
applies to the following autoconf test in configure.in:
  AC_CHECK_FUNC(socket, :, [      
  dnl hopefully we won't include too many libraries
          AC_CHECK_LIB(socket, main)
          AC_CHECK_LIB(net, main)
          AC_CHECK_LIB(nsl_s, main)
          AC_CHECK_LIB(nsl, main)
          AC_CHECK_LIB(inet, socket)
          AC_CHECK_LIB(gen, main)
  ])

Much better would be the following:
  AC_CHECK_FUNC(gethostent, , AC_CHECK_LIB(nsl, gethostent))
  AC_CHECK_FUNC(setsockopt, , AC_CHECK_LIB(socket, setsockopt))

We have tested this on Solaris 2.5.1, 2.6, 7, 8, HP-UX 11.00, Tru64 UNIX 4.0D,
5.0A, 5.1, IRIX 6.2, 6.5, and AIX 4.3.2 successfully.

Patch at:
  ftp://ftp.thewrittenword.com/outgoing/pub/openldap-2.0.21-2.patch