src: Add util::array_size
Add reserved bits to header and frames

Currently reserved bit is always set to 0.  The addition of reserved
bit is for future extension.
tests: Remove debug output
src: Add missing SETTINGS ID to debug output

SETTINGS_MAX_FRAME_SIZE and SETTINGS_MAX_HEADER_LIST_SIZE are 2
missing SETTINGS IDs and now they are shown correctly.
Update sphinx_rtd_theme
Bump up version number to 0.6.0 and LT revision to 5:0:0
Update man pages
Add Wdocumentation Clang Flag