Reported by the new script 'scripts/copyright.pl'. The script has a
regex whitelist for the files that don't need copyright headers.

Removed three (mostly usesless) README files from docs/

Closes #5141

This change allows runtests.pl to be run from the CMake builddir:

    export srcdir=/tmp/curl/tests;
    perl -I$srcdir $srcdir/runtests.pl -l

In order to make this possible, all test cases have been moved from
Makefile.am to Makefile.inc.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>

Similar to test 76 but that test's URL has a slash just no file name
part.

Option --pinnedpubkey takes a path to a public key in DER format and
only connect if it matches (currently only implemented with OpenSSL).

Provides CURLOPT_PINNEDPUBLICKEY for curl_easy_setopt().

Extract a public RSA key from a website like so:
openssl s_client -connect google.com:443 2>&1 < /dev/null | \
sed -n '/-----BEGIN/,/-----END/p' | openssl x509 -noout -pubkey \
| openssl rsa -pubin -outform DER > google.com.der

Verifies that the change in 68f0166a92 works as intended and that
different HTTP auth credentials to the same host still re-uses the
connection properly.

Updated the docs to clarify and the code accordingly, with test 1528 to
verify:

When CURLHEADER_SEPARATE is set and libcurl is asked to send a request
to a proxy but it isn't CONNECT, then _both_ header lists
(CURLOPT_HTTPHEADER and CURLOPT_PROXYHEADER) will be used since the
single request is then made for both the proxy and the server.