Otherwise, clang on Cygwin64 warns:
curl_ntlm_core.c:525:35: error: array subscript is of type 'char'
[-Werror,-Wchar-subscripts]
    dest[2 * i] = (unsigned char)(toupper(src[i]));
                                  ^~~~~~~~~~~~~~~
/usr/include/ctype.h:152:25: note: expanded from macro 'toupper'
      (void) __CTYPE_PTR[__x]; (toupper) (__x);})
                        ^~~~

Closes https://github.com/curl/curl/pull/1539

Closes #1534

GCC 7 complained:
‘*’ in boolean context, suggest ‘&&’ instead [-Wint-in-bool-context]

This fixes the following warning with CURL_DISABLE_CRYPTO_AUTH,
as seen in the autobuilds:

curl_sasl.c:417:9: warning: unused variable 'serverdata'
[-Wunused-variable]

cyassl/ssl.h needs the macros from cyassl/options.h, so define them
before including cyassl/ssl.h the first time, which happens in
urldata.h.
This broke the build on Ubuntu Xenial, which comes with WolfSSL 3.4.8
and therefore redefines the symbols from cyassl/options.h instead of
including the header.

Closes https://github.com/curl/curl/pull/1536

Closes #1532

Found when updating test 1395, which I did to increase test coverage of
this source file...

Closes #1535

mbedtls_x509_crt_profile_fr is only used locally.
This fixes a missing-variable-declarations warning with clang.

Unaligned access is on purpose here and the warning is harmless on
affected architectures. GCC knows that, while clang warns on all
architectures.

Closes #1529

Closes #1530

... the torture ones are commented out only because they are slooooow.

Closes #1528

... and update the certinfo.c example accordingly.

Fixes https://github.com/curl/curl/issues/846

... so that they get the required "struct curl_tlssessioninfo **"
arguments.

Fixes #1524

Otherwise, they are removed in the final configure file.
Also changed sed to "$SED" like in most other calls in this file.

"clang -dumpversion" always returns "4.2.1", the GCC version that clang
was initially compatible to. Use "clang -v" instead, which returns the
actual clang version.

Fixes https://github.com/curl/curl/issues/1522
Closes https://github.com/curl/curl/pull/1523

... since closesocket is a function in WinSock.

Reported-by: Marcel Raad
Bug: https://github.com/curl/curl/commit/55fcb8485914700132fd1854c9509b66c955efbe#co
mmitcomment-22347818

Use CURLMcode for variable 'res' and cast to int where necessary
instead of the other way around. Other tests do the same.

This fixes the following clang warning:
lib583.c:68:15: warning: cast from function call of type 'CURLMcode' to
non-matching type 'int' [-Wbad-function-cast]

Reported-by: Gisle Vanem

clang 2.9+ supports -Wshift-sign-overflow, which warns about undefined
behavior on signed left shifts when shifting by too many places.

Ref: https://github.com/curl/curl/issues/1516
Closes https://github.com/curl/curl/pull/1517

wolfSSL configure script relevant changes from 3.10 to 3.11:

- Async threading support added; disabled by default without async
  crypto, which continues to be disabled by default.

wolfSSL configure script relevant changes from 3.11 to 3.11.1 (beta):

- TLS 1.3 beta support added; disabled by default.

For experimenting I put in a comment block the defines needed to enable
TLS 1.3 support (ie the equivalent of --enable-tls13).

Fixes #1208