Fixed a problem with sending usernames and passwords that contain
backslash, quotation mark and space characters.

... 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.