Stdio.File: Support buffering in read().

Stdio.File()->read() now reads from the input buffer if there is one,
and then from the actual fd.
We don't test for C89 functions anymore.
Fixed warning.
Fixed warning.
Added GeneralizedTime.
Support initialization from calendar object.
Support dates beyond 2050.
No parameters means one element less, not a Null element.
No parameters means one element less, not a Null element.
Verify that no additional payload is hidden in ASN.1 structures.
No, I had it right the first time. (Though DSA wasn't.)
Simple testcase for secure_der_decode.