This adds a crypto framework for boot-time code without the size restrictions to which BIOS code is subject. The framework is designed to allow new ciphers to be added relatively easily.

Note: it is probable that this code will be replaced in the mid-term future. There is talk of a crypto overhaul, but this will not take place in any timeline suitable for GELI integration.

This has already been tested for both AES-CBC and AES-XTS in testing of the GELI boot code. Its present form is unmodified from the last successful test.