Closes #3752

To aid debugging better.

Commit 9081014c fixed most of the confusing issues between scope id and
scope however 844896d0 added bad limits checking assuming that the scope
is being set and not the scope id.

I have fixed the documentation so it all refers to scope ids.

In addition Curl_if2ip refered to the scope id as remote_scope_id which
is incorrect, so I renamed it to local_scope_id.

Adjusted-by: Daniel Stenberg

Closes #3655
Closes #3765
Fixes #3713

Only allow well formed decimal numbers in the input.

Document that the number MUST be between 1 and 65535.

Add tests to test 1560 to verify the above.

Ref: https://github.com/curl/curl/issues/3753
Closes #3762

- Remove the lines in winbuild/Makefile.vc that generate an error with
  multiple SSL backends.

- Add /DCURL_WITH_MULTI_SSL in winbuild/MakefileBuild.vc if multiple SSL
  backends are set.

Closes https://github.com/curl/curl/pull/3772

Since the mesalink build started to fail on travis, even though we build
a fixed release version, we disable it to prevent it from blocking
progress.

Closes #3767

Without this, detecting and avoid reusing a closed TLS connection
(without a previous GOAWAY) when doing HTTP/2 is tricky.

Reported-by: Tom van der Woerdt
Fixes #3750
Closes #3763

Functionally this doesn't change anything as we still use the username
for both the authorisation identity and the authentication identity.

Closes #3757

Based-on-code-by: Poul T Lomholt

Since a few code paths actually update that data.

Fixes #3753
Closes #3761

Reported-by: Poul T Lomholt

Remove the code too. The functionality has been disabled in code since
7.62.0. Setting this option will from now on simply be ignored and have
no function.

Closes #3654

Reduces the time needed for the other jobs a little.

Closes https://github.com/curl/curl/pull/3721

Reduces the time needed for the other jobs a little.

Closes https://github.com/curl/curl/pull/3721

Reduces the time needed for the other jobs a little.

Closes https://github.com/curl/curl/pull/3721

Reduces the time needed for the other jobs a little.

Closes https://github.com/curl/curl/pull/3721

Reduces the time needed for the other jobs a little.

Closes https://github.com/curl/curl/pull/3721

Reduces the time needed for the other jobs a little.

Closes https://github.com/curl/curl/pull/3721

This reduces the GCC job runtimes a little and it's needed to
selectively update clang builds to xenial.

Closes https://github.com/curl/curl/pull/3721

Closes https://github.com/curl/curl/pull/3725

- remove unused variables
- declare conditionally used variables conditionally
- suppress unused variable warnings in the CMake tests
- remove dead variable stores
- consistently use WIN32 macro to detect Windows

Closes https://github.com/curl/curl/pull/3739

Make functions no-ops if neither both USE_THREADS_POSIX and
HAVE_PTHREAD_H nor both USE_THREADS_WIN32 and HAVE_PROCESS_H are
defined. Previously, if only one of them was defined, there was either
code compiled that did nothing useful or the wrong header included for
the functions used.

Also, move POLARSSL_MUTEX_T define to implementation file as it's not
used externally.

Closes https://github.com/curl/curl/pull/3739

These variables are only conditionally initialized.

Closes https://github.com/curl/curl/pull/3739

Closes https://github.com/curl/curl/pull/3739

Consistently use one blank line between blocks.

Closes https://github.com/curl/curl/pull/3739

Always use the ANSI version of FormatMessage as we don't have the
curl_multibyte gear available here.

Closes https://github.com/curl/curl/pull/3758

The stripcredentials unittest fails to compile on platforms without
xattr support, for example the Solaris member in the buildfarm which
fails with the following:

  CC unit1621-unit1621.o
  CC ../libtest/unit1621-first.o
  CCLD unit1621
  Undefined first referenced
  symbol in file
  stripcredentials unit1621-unit1621.o
  goto problem 2
  ld: fatal: symbol referencing errors. No output written to .libs/unit1621
  collect2: error: ld returned 1 exit status
  gmake[2]: *** [Makefile:996: unit1621] Error 1

Fix by excluding the test on such platforms by using the reverse
logic from where stripcredentials() is defined.

Closes #3759
Reviewed-by: Daniel Stenberg <daniel@haxx.se>

Stick to "Schannel" everywhere - follow up to 180501cb.

This fixes GSSAPI builds with the libraries in a non-standard location.
The testing for recv() were failing because it failed to link
the Kerberos libraries, which are not needed for this or subsequent
tests.

fixes #3743
closes #3744

With CMAKE_TRY_COMPILE_TARGET_TYPE set to STATIC_LIBRARY, the try_compile()
(which is used by check_c_source_compiles()) will build static library
instead of executable. This avoids linking additional libraries in and thus
speeds up those checks a little.

This commit also avoids #3743 (GSSAPI build errors) on itself with cmake
3.6 or above. That issue was fixed separately for all versions.

Ref: #3744

- Remove nneeded include_regular_expression.
  It was setting what is already a default.

- Remove duplicated include.

- Don't check for pre-3.0.0 CMake version.
  We already require at least 3.0.0, so it's just clutter.

Ref: #3744