RELEASE-NOTES: synced with 87cf677eca55

Added 11 bugs and 7 contributors
curl_easy_setopt.3: HTTP header with no content

Update the documentation on how to specify a HTTP header with no
content.
axtls: honor disabled VERIFYHOST

When VERIFYHOST == 0, libcurl should let invalid certificates to pass.
cert_stuff: remove code duplication in the pkcs12 logic
cert_stuff: avoid double free in the PKCS12 code

In the pkcs12 code, we get a list of x509 records returned from
PKCS12_parse but when iterating over the list and passing each to
SSL_CTX_add_extra_chain_cert() we didn't also properly remove them from
the "stack", which made them get freed twice (both in sk_X509_pop_free()
and then later in SSL_CTX_free).

This isn't really documented anywhere...

Bug: http://curl.haxx.se/bug/view.cgi?id=1236
Reported-by: Nikaiw
multi_socket: reduce timeout inaccuracy margin

Allow less room for "triggered too early" mistakes by applications /
timers on non-windows platforms. Starting now, we assume that a timeout
call is never made earlier than 3 milliseconds before the actual
timeout. This greatly improves timeout accuracy on Linux.

Bug: http://curl.haxx.se/bug/view.cgi?id=1228
Reported-by: Hang Su
Curl_output_digest: support auth-int for empty entity body

By always returning the md5 for an empty body when auth-int is asked
for, libcurl now at least sometimes does the right thing.

Bug: http://curl.haxx.se/bug/view.cgi?id=1235
Patched-by: Nach M. S.
KNOWN_BUGS: #82 failed build with Borland compiler