Don't ask.

Oh well, if you want to know: For some people, like me, Cygwin and its
Perl run into horrible trouble with the fork() emulation when building
OpenSSL. (But my Cygwin works fine for all else in the build. Go
figure.)

So I came up with a way to use prebuilt OpenSSL binaries. Not to be
used for release builds, of course (and the configury checks for
that), as long as our policy is to build all we can from sources.

Change-Id: Ic303bdf0c620c5122aca3d646fa1f0587221e70f