Also erase generated .rst files on `make clean`.

Patch from Dave Beckett

We need paddings regardless of payload and frame boundary to mitigate
certain attacks.

Since we handles CONTINUATION internally, we don't show FLAG_PAD_HIGH
and PAD_LOW flags of HEADERS in nghttp/nghttpd. We just show the
total paddings in HEADERS + CONTINUATION.

The only drawback is that page source only contains include
directive. We disabled page source for now.

* Use 1 Huffman code table for both request and response
* Remove complicated deflater side table size management
* Add encoding context update
* Fix memory leak in inflater

This may help the pathological situation where window is too small.