The encoder is not required to send dynamic table size update if the
table size is not changed from the previous value after accepting new
maximum value.

This will improve performance since we can avoid indirect call of
internal functions.  The downside is we now require libnghttp2 static
library to run unit tests.

Merge branch 'nghttpx-tls-dyn-rec-config' of https://github.com/LPardue/nghttp2 into LPardue-nghttpx-tls-dyn-rec-config

Update doc for Chromium HTTP/2 proxy support

This change adds subsecond rate period support to h2load.  Now
--rate-period option only accepts integer, but it can be followed by
units.  Currently, h, m, s, and ms are supported, which are hours,
minutes, seconds, and milliseconds respectively.  The underlying
functionality and usecase are already extensively used in nghttpx.