macro (modeled after similar macros provided with "autoconf") to check
whether "struct sockaddr" has an "sa_len" member, and defines or
undefines "HAVE_SA_LEN" appropriately. Use it instead of
"AC_LBL_SOCKADDR_SA_LEN", and use "HAVE_SA_LEN" instead of
"HAVE_SOCKADDR_SA_LEN".
svn path=/trunk/; revision=96
Guy Harris