Signal: restore handler for SIGPIPE.

This problem was introduced on commit 84fa79eb. Without the SIGPIPE handler
the server will stop working when the Kernel trigger a SIGPIPE because of a
remote socket disconnection.

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: If-Modified-Since now allow clients from the future.

Before this patch the server did not respect a conditional
If-Modified-Since if the value was higher than the system server
date. This patch makes this pass, not a bug but make it more
friendly with Checker tools.

This patch also fix a QA script involved.

Signed-off-by: Eduardo Silva <eduardo@monkey.io>