configure: Fixed inclusion of krb5 when CURL_DISABLE_CRYPTO_AUTH is defined

Commit fe0f8967bf fixed a problem with krb5 not being defined as a
supported feature when HAVE_GSSAPI is defined, however, it should
only be included if CURL_DISABLE_CRYPTO_AUTH is not set, like when
SPNEGO is listed as a feature.
http2: Deal with HTTP/2 data inside response header buffer

Previously if HTTP/2 traffic is appended to HTTP Upgrade response header
(thus they are in the same buffer), the trailing HTTP/2 traffic is not
processed and lost.  The appended data is most likely SETTINGS frame.
If it is lost, nghttp2 library complains server does not obey the HTTP/2
protocol and issues GOAWAY frame and curl eventually drops connection.
This commit fixes this problem and now trailing data is processed.
http2: fix switched macro when http2 is not enabled
RELEASE-NOTES: synced with 2ee3c63b13
test22: expand a backtick command

This is the only user of the backtick operator in the command. As the
commands will soon not be executed by a shell anymore (but by perl),
replace the command with its output.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
CMake: Restore order-dependent header checks

Revert commit 1269df2e3b (Cmake: Don't check for all headers each
time, 2014-08-15) and add a comment explaining the purpose of the
original code.

The check_include_file_concat macro is intended to be called multiple
times on a sequence of possibly dependent headers.  Later headers
may depend on earlier headers to provide declarations.  They cannot
be safely included independently on some platforms.

For example, many POSIX APIs document including sys/types.h before some
other headers.  Also on some OS X versions sys/socket.h must be included
before net/if.h or the check for the latter will fail.

Signed-off-by: Brad King <brad.king@kitware.com>
CMake: Restore order-dependent library checks

Revert commit 2257deb502 (Cmake: Avoid cycle directory dependencies,
2014-08-22) and add a comment explaining the purpose of the original
code.

The check_library_exists_concat macro is intended to be called multiple
times on a sequence of possibly dependent libraries.  Later libraries
may depend on earlier libraries when they are static.  They cannot be
safely linked in reverse order on some platforms.

Signed-off-by: Brad King <brad.king@kitware.com>