Reinstate IPV6 build variable that got removed.

Failed to commit this file changes along with the others.

warning C4146: unary minus operator applied to unsigned type, result still unsigned

Ensure that spurious results from system's getaddrinfo() ares not propagated
by Curl_getaddrinfo_ex() into the library.

Also ensure that the ai_addrlen member of Curl_getaddrinfo_ex()'s output linked
list of Curl_addrinfo structures has appropriate family-specific address size.

... not the proxy port.  It makes no difference unless a proxy is used.

Winsock builds clobber some errno.h defines in setup_once.

This showed a problem when running the test out-of-tree, so
an include path is now being added to pick up the generated
curlbuild.h file.

On Windows, translate WSAGetLastError() to errno values as GNU
TLS does it internally, too. This is necessary because send() and
recv() on Windows don't set errno when they fail but GNU TLS
expects a proper errno value.

Bug: http://curl.haxx.se/bug/view.cgi?id=3110991

Temporarily, When cross-compiling with gcc 3.0 or later, enable strict aliasing
rules and warnings. Given that cross-compiled targets autobuilds do not run the

If --librtmp was specified but pkg-config could not find the librtmp
file, we would have undefined symbols when linking curl.

We prevent this error by disabling this case as suggested on the mailing
list.

When no timeout is set, we call the socket_ready function with a timeout
value of 0 during handshake, which makes it loop too much/fast in this
function. It also made this function return CURLE_OPERATION_TIMEDOUT
wrongly on a slow handshake.

However, the particular bug report that highlighted this problem is not
solved by this fix, as this fix only makes the more proper error get
reported instead.

Bug: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=594150
Reported by: Johannes Ernst

This makes it easier to spot the enum values from the variables.
Removed some unneeded DEBUGASSERT added in the previous commit.

While changing Curl_sec_read_msg to accept an enum protection_level
instead of an int, I went ahead and fixed the usage of the associated
fields.

Some code was assuming that prot_clear == 0. Fixed those to use the
proper value. Added assertions prior to any code that would set the
protection level.