non-openssl build fixes

[Damien Miller]

Thanks! Could I ask you to please create a bug at
https://bugzilla.mindrot.org and attach the patches to it?

-d

On Wed, 22 Apr 2015, Reuben Hawkins wrote:

> The attached patches fixes and cleans up the build when configured
> with --without-openssl.
> 
> Summary:
> * Fix KEX_SERVER_ENCRYPT macro in myproposal.h
> * Fix unresolved symbols in ssh-keygen.c
> * Isolate openssl code and extend WITH_OPENSSL wrappers around it
> * Make ed25519 default key type in ssh-keygen when configured --without-openssl
>