if no error was raised by the API but the SecIdentityRef was null

Fixes #1450

Reported-by: wyattoday at github
Fixes #1487

Closes #1400

follow-up to 5ddad099

... and support and additional "security patched" date for those who
enhance older versions that way. Pass on the define CURL_PATCHSTAMP with
a date for that.

Building with non-release headers shows the date as [unreleased].

Also: this changes the date format generated in the curlver.h file to be
"YYYY-MM-DD" (no name of the day or month, no time, no time zone) to
make it easier on the eye and easier to parse. Example (new) date
string: 2017-05-09

Suggested-by: Brian Childs

Closes #1474

Some code (e.g. Curl_fillreadbuffer) assumes that this buffer is not
exceedingly tiny and will break if it is. This same check is already
done at run time in the CURLOPT_BUFFERSIZE option.

... I found them in the commit logs from the early years

Also removed a TODO suggesting caching the precheck results. Tests
showed this would save about 0.1 sec on the total test run time on a
relatively modern system, an unnoticeable gain at the cost of longer and
more complicated code. There would also be a danger that a cached test
result would be inappropriately returned, such as when other test
dependencies (like environment variables) are different or when the
precheck causes side effects (like filesystem changes).

... and delete trailing whitespace

Fixes #1484

The function IsPipeliningPossible() would return TRUE if either
pipelining OR HTTP/2 were possible on a connection, which would lead to
it returning TRUE even for POSTs on HTTP/1 connections.

It now returns a bitmask so that the caller can differentiate which kind
the connection allows.

Fixes #1481
Closes #1483
Reported-by: stootill at github

Tested with servers: IIS 7.5; OpenSSL 1.0.2.

Closes https://github.com/curl/curl/pull/1475

clang 5.0 complains:
possible misuse of comma operator here [-Wcomma]

clang 5.0 complains:
possible misuse of comma operator here [-Wcomma]

Change the comma to a semicolon to fix that.

... since the total amount is low this is faster, easier and reduces
memory overhead.

Also, Curl_expire_done() can now mark an expire timeout as done so that
it never times out.

Closes #1472

 A) reduces the timeout lists drastically

 B) prevents a lot of superfluous loops for timers that expires "in vain"
    when it has actually already been extended to fire later on

@MarcelRaad noted that `test1399` causes infinite loop on MinGW.
Looking into this, seems like it is related to how Windows handles
CRLF. See https://github.com/curl/curl/commit/9e093f by @mback2k.
Removing `test1399` as it's identical to `test1326` then with such a
fix.

Test 1399 was broughy by commit 862b02f8

Closes #1478

Include the test number in the names of files written out by tests to
reduce the chance of accidental duplication and to make it more clear
which test is associated with which file.

This is already added by the test suite; it's not clear why all these
tests had it, unless it's cargo-culting.

Avoid casting away low-level const.

... to really make sure the boundary fits in the target buffer.

Fixes unused parameter 'buflen' warning.

Reported-by: Michael Kaufmann
Bug: https://github.com/curl/curl/pull/1468#issuecomment-300078754

... using the docs/cmdline-opts/gen.pl script, so that we get all the
command line option documentation from the same source.

The generation of the list has to be done manually and pasted into the
source code.

Closes #1465

When the random seed is purposely made predictable for testing purposes
by using the CURL_ENTROPY environment variable, process that data in an
endian agnostic way so the the initial random seed is the same
regardless of endianness.

- Change Curl_rand to write to a char array instead of int array.

- Add Curl_rand_hex to write random hex characters to a buffer.

Fixes #1315
Closes #1468

Co-authored-by: Daniel Stenberg
Reported-by: Michael Kaufmann

Otherwise, subsequent uses of stunnel overwrite the configuration file
of previous invocations so they can no longer be inspected.

Commit 481e0de0 changed the variable
type from int to size_t, so don't cast the result of strlen to int
anymore.

alarm's argument is unsigned.

long is 32 bits while size_t is 64 bits on MinGW-w64, so
typecheck-gcc.h complains when using size_t for a long option.
Also, curl_socket_t is unsigned long long rather than int.

... to also make it update when we remove files, like we did for
--environment in commit a8e388dd.

Avoids narrowing conversion warnings because rlim_t is usually
unsigned long.

Closes https://github.com/curl/curl/pull/1469

The first argument to select is an int, while curl_socket_t is
unsigned long long when using WinSock. It's ignored anyway [1].

[1] https://msdn.microsoft.com/en-us/library/windows/desktop/ms740141.aspx