Use needed -m ABI flags in --via-amalgamation builds
Fix gcc cpuid call
Make Simd_Scalar of generic size
Add info for SRP-GCM
Fix TLS-SRP example
Set -m flags for rdrand.cpp. Update compiler ISA flags
Add Threefish-512 in AVX2

Tested using Intel's SDE, but no idea how fast it will be on hardware.