Add verification of compact signatures.

[sowbug]

Per discussion in #18.

[sowbug]

I forgot to update the error message at the top of openssl.rb. "Skipping FFI needed for OpenSSL_EC.regenerate_key" should either be generalized or else list every public method this module implements.

[lian]

yea good note. i'm currently merging and fixing the memory leaks in that new method. going to push soon.

[lian]

Thanks for your contribution! adding signmessage would be nice too :)

[mhanne]

Nice! AFAIK, an FFI::MemoryPointer frees itself, unless autorelease = false is set.
That it uses a CDataStream is a bit unfortunate. FWIW, I've quickly tried changing the #wrap_message_in_magic to something like this:
out = "\x18Bitcoin Signed Message:\n"
message.split("").each_slice(255) {|c| out << c.size.chr; out << c.join }
out
... but that doesn't seem to be how it works.