For user_settings.h builds, .S assembly files need to include user_settings.h
in order to get the defines used by the build. However, a user_settings.h may
contain code only understood by a C compiler and not the assembler (e.g. a
typedef). This commit makes it so our autotools and CMake builds produce a file
user_settings_asm.h when doing a user_settings.h build. This generated header
contains only the preprocessor directives from the user_settings.h. As a result,
it can be safely included by our assembly code files.
Add x86_64 assembly code:
- BMI2
- AVX2 (using ymm, slower than BMI2)
- AVX2 of 4 similtaneous hashes
Add SHAKE128 functions and tests.
Add Absorb and Squeeze functions for SHAKE128 and SHAK256 and tests.
Add doxygen for SHA-3 and SHAKE functions.
Update other generated x86_64 assembly files to include settings.h.
