std.crypto.random: introduce fork safety

Everybody gets what they want!

 * AT_RANDOM is completely ignored.
 * On Linux, MADV_WIPEONFORK is used to provide fork safety.
 * On pthread systems, `pthread_atfork` is used to provide fork safety.
 * For systems that do not have the capability to provide fork safety,
   the implementation falls back to calling getrandom() every time.
 * If madvise is unavailable or returns an error, or pthread_atfork
   fails for whatever reason, it falls back to calling getrandom() every
   time.
 * Applications may choose to opt-out of fork safety.
 * Applications may choose to opt-in to unconditionally calling
   getrandom() for every call to std.crypto.random.fillFn.
 * Added `std.meta.globalOption`.
 * Added `std.os.madvise` and related bits.
 * Bumped up the size of the main thread TLS buffer. See the comment
   there for justification.
 * Simpler hot path in TLS initialization.

0 files changed, 0 insertions, 0 deletions