User experience improvements

I would propose you a couple little enhancements to improve the user experience.
I wasn't able to build OpenSSL on my system, and after some research I've found that the perl version available on the system may affect the issue of the build. So I've added a suggestion to the README file.

Secondarily, the build-openssl.bat script will fail when no argument is passed, because of unescaped redirection characters. Build-openssl.bat is expected to print an *usage description* when it is invoked without parameters. Instead, it will print an unuseful message, like

    < was unexpected