Use PowerPC unaligned loads and stores with Power8. Formerly we were using Power7 as the floor because the IBM POWER Architecture manuals said unaligned loads and stores were available. However, some compilers generate bad code for unaligned loads and stores using `-march=power7`, so bump to a known good.
The ParameterBlocks for BLAKE2 had undefined behavior. We relied on the compiler packing the bytes in the structure, then we used the first byte as the start of an array.
This rewrite does things correctly. We don't memset the structure, and we don't treat the structure as a contiguous array.
The CORE function provides the implementation for ChaCha_OperateKeystream_ALTIVEC, ChaCha_OperateKeystream_POWER7, BLAKE2_Compress32_ALTIVEC and BLAKE2_Compress32_POWER7. Depending on the options used to compile the source files, either POWER7 or ALTIVEC will be used.
This is needed to support the "new toolchain, ancient hardware" use case.
