Move ECC SSL extensions to the end.
WebSphere Application Server 7.0 appears to be intolerant of an empty
extension at the end. To that end, also ensure we never send an empty
padding extension.
Fix limit checks in ssl_add_clienthello_tlsext and
ssl_add_serverhello_tlsext.
Some of the limit checks reference p rather than ret. p is the original
buffer position, not the current one. Fix those and rename p to orig so
it's clearer.
Initial fork from f2d678e6e89b6508147086610e985d4e8416e867 (1.0.2 beta).
(This change contains substantial changes from the original and
effectively starts a new history.)
