nghttp2_bufs_remove: Prevent NULL from being passed to memcpy
Code cleanup
Add AX_CHECK_COMPILE_FLAG (from Autotools packages)

It's fix the build with Clang and --enable-werror, don't support -WClobberred and display error about unknown warning option
error: unknown warning option '-Wclobbered'; did you mean '-Wconsumed'? [-Werror,-Wunknown-warning-option]
Add some news CFLAGS:
* -Wpragmas
* -Wunreachable-code
* -Wpedantic
* -Waddress
* -Wattributes
* -Wdiv-by-zero
* -Wheader-guard
Fix bug HPACK deflater does not send context update after table size change
Add NGHTTP2_DEFAULT_HEADER_TABLE_SIZE macro

Use this macro in Python sources.  Python module constant
HD_DEFLATE_HD_TABLE_BUFSIZE_MAX was renamed as
DEFLATE_MAX_HEADER_TABLE_SIZE since the previous name was awkward.
nghttpd: Fix compiler warning
Merge branch 'add_check_compile_flag' of https://github.com/alagoutte/nghttp2 into alagoutte-add_check_compile_flag
Fix compile error with clang -Wunreachable-code
Check max SETTINGS_HEADER_TABLE_SIZE in nghttp2_iv_check()

Hide NGHTTP2_MAX_HEADER_TABLE_SIZE from public API.  Now it is defined
as ((1u << 31) - 1) in nghttp2_frame.h, which is sufficiently big
enough.
Return NGHTTP2_ERR_BUFFER_ERROR from nghttp2_hd_{deflate,inflate}_hd

It is generally useful to know what is the cause of the error.  Since
we expose HPACK API, it is friendly to tell application the
insufficient buffer size is a culprit.
Add missing library error code to nghttp2_error()
Remove outdated comment
Ec2
test2
test3
test4
test5