Remove all threading/locking code

[briansmith]

• Fix Issue Replace use of crypto/rand with more direct use of OS RNG #58, Replace use of crypto/rand, should remove the use of thread-local storage and static locks in the Rand code.
• Fix Issue Simplify RSA signing code #99, Simplify RSA Signing Code, should remove the use of locks in the RSA code.
• Move the CRYPTO_once- and/or static-initializer- based logic for the CPUID functionality to Rust-managed code.
• Remove all the threading/locking primitives in crypto/internal.h and crypto/thread*.

[briansmith]

This was done!