Merge pull request #199 from marcosfrm/comp-libs-up

Update bundled compression libraries

Merge pull request #188 from marcosfrm/harden-1

Explicitly disable PIE with harden=0

Don't propagate exceptions in Observable::notify()

Make leveldb optional again. re:#182

Added timeout option to httpclient tool

Reopen Nameserver connection on write failure to fix macOS issue, re:…

…#337

Improve timeseries effiency when handling large result sets

Use all DNS servers at once, query DNS in correct order, return HTTP:…

…:Conn from Client::send(), Fix for ACMEv2::Account

Use all DNS servers at once, query DNS in correct order, return HTTP:…

…:Conn from Client::send(), Fix for ACMEv2::Account

Option constraints and help