client: do not allocate 4M on the stack, statically in an threaded env

4M was enough to cause stack overflows for me when running the client.
Such buffers should be allocated on the heap.

Also, in a threaded environment (one munin client is spawned for each
incoming connection), you do not want this buffer to be static, or
threads might trash each other data.
server: handle the case where inbound address cannot be resolved

Error checking FTW.
service: extend -run delay to 100 seconds

10 seconds is a bit short in a build, start, do something munin server
side development cycle. You can just CTRL-C the process when done
testing.
service: flush standard streams when logging in -run mode

Otherwise the log entries are never displayed should some unhandled
exception happen (like a stack overflow).
Merge pull request #46 from pmezard/fix-client-buffer-allocation

Fix client buffer allocation