Use larger nslcd send buffers

By using bigger write buffers in nslcd we reduce the number of writes in
nslcd and consequently the number of reads in the NSS and PAM modules
for bigger responses.

This reduces the number of system calls that are made during a request
and brings a small performance improvement that is mainly measurable in
the NSS module. A measurement showed 30-80% reduction in the number of
system calls in the NSS module and around 10% reduction in CPU usage
(CPU time, only small reduction in wallclock time).

Thanks John Sullivan for pointing this out.
Upgrade to automake 1.14