Optimized Picnic implementation version 3.0.8

• Prefix compat function implementations with picnic_.
• Use OQS instruction set checking functions.
• Use OQS implementations of aligned_alloc, aligned_free, explicit_bzero, and timingsafe_bcmp.
• Install cmake configuration files.

Optimized Picnic implementation version 3.0.7

• Various changes to improve OQS integration.
• Require cmake version 3.10.

Optimized Picnic implementation version 3.0.6

• Reduce size of global parameters for instance specification to 12 bytes per instance.
• Provide compat implementation of clz on MSVC using _BitScanReverse.
• Do not assume that aligned_alloc is available on MSVC.