It is a programming error, not a runtime error, if we attempt to use
block ciphers with an incorrect blocksize, so use an assert() rather
than an error status return.

The various types of cryptographic algorithm are fundamentally
different, and it was probably a mistake to try to handle them via a
single common type.

pubkey_algorithm is a placeholder type for now.

Although the nature of the hack is essentially unchanged, this allows
us to remove the hardcoded assumption in tls.c that the RX cipher is
AES.

Use our own, more robust, ASN.1 parsing routines to extract the RSA
public key from a server certificate.  Remove the now-unused AXTLS
ASN.1 parser.

gcc 4.4 adds another few warnings, and also seems to complain if we
place %ebp in the clobber list for any inline asm.

separate xfer method.

Add missing .alloc_iob entries to several xfer_interface_operations
structures.

algorithms; we only need the pubkey check disabled (and only because
pubkey algorithms are not yet integrated into the crypto_algorithm
subsystem).