Implement Point#mul

[headius]

Work in progress. Fixes #306.

[alextwoods]

I think there is at least one other math operation on ECPoint that this change now makes it easy to support: add

[headius]

Yes I'll do add in another PR!

[headius]

Initial implementation is in place and appears to work for your simple example:

[] jruby-openssl $ jruby -Ilib blah.rb
"\x04|\xF2{\x18\x8D\x03O~\x8AR8\x03\x04\xB5\x1A\xC3\xC0\x89i\xE2w\xF2\e5\xA6\vH\xFCGf\x99x\awU\x10\xDB\x8E\xD0@)=\x9A\xC6\x9Ft0\xDB\xBA}\xAD\xE6<\xE9\x82)\x9E\x04\xB7\x9D\"xs\xD1"
[] jruby-openssl $ ruby33 blah.rb  
"\x04|\xF2{\x18\x8D\x03O~\x8AR8\x03\x04\xB5\x1A\xC3\xC0\x89i\xE2w\xF2\e5\xA6\vH\xFCGf\x99x\awU\x10\xDB\x8E\xD0@)=\x9A\xC6\x9Ft0\xDB\xBA}\xAD\xE6<\xE9\x82)\x9E\x04\xB7\x9D\"xs\xD1"

I'm comparing uncompressed octet string output from each here. Better confirmation would be to run the related CRuby openssl tests, but there are other issues preventing us from running test_ec_point_mul and test_ec_point_add (4-arg constructor for Group is not implemented). This is at least a good start!

[headius]

@alextwoods This now has add. Would you be able to test this branch against your code, or at least a more complex example? It will take more work to fill out Group logic to support the test in CRuby.

@kares Review please!

[alextwoods]

This works great! The AWS SDK For Ruby has a fairly extensive test suite for a signing algorithm based off of ECC and relies on the mul method (sigv4a) - this change passes all of our tests :-)

[headius]

this change passes all of our tests

Gotta admit I'm surprised! But I think we can merge this in if @kares is ok with it. Fair warning: it's probably not going to be live until 0.15.0 releases unless we backport to 0.14 and do another release there.

[kares]

There seems to be a regression, otherwise LGTM

[headius]

I would like to add Point#add as well but hoping to get the related tests running first. That depends on getting #309 working.