... on Snow Leopard and Lion

Snow Leopard introduced the SSLSetSessionOption() function, but it
doesn't disable peer verification as expected on Snow Leopard or
Lion (it works as expected in Mountain Lion). So we now use sysctl()
to detect whether or not the user is using Snow Leopard or Lion,
and if that's the case, then we now use the deprecated
SSLSetEnableCertVerify() function instead to disable peer verification.

WinSock select() does not support standard file descriptors,
it can only check SOCKETs. The following function is an attempt
to create a select() function with support for other handles.

... and have it take a proper 'struct connectdata *' as first argument

... it also clobbered the 'result' return value so that it wouldn't
return the error back to the parent function properly, which broke test
809 when run with 'multi-always'.

When prefixing a path with /~/ it is supposed to be used relative to the
user's home directory but it didn't work. Now we cut off the entire
three byte sequenct "/~/" which seems to be how OpenSSH does it.

Bug: http://curl.haxx.se/bug/view.cgi?id=1173
Reported by: Balaji Parasuram

Also reverts commit f254c59d

The Clang compiler found a few implicit conversion problems that have
now been fixed.

Issue: When building a 32bit target with large file support HP-UX
<sys/socket.h> header file may simultaneously provide two different
sets of declarations for sendfile and sendpath functions, one with
static and another with external linkage. Given that we do not use
mentioned functions we really don't care which linkage is the
appropriate one, but on the other hand, the double declaration emmits
warnings when using the HP-UX compiler and errors when using modern
gcc versions resulting in fatal compilation errors.

Mentioned issue is now fixed as long as we don't use sendfile nor
sendpath functions.

Inclusion of top two most included header files now done in setup_once.h