Summary

Adds the low-level virtual-memory and thread-control primitives needed for cross-platform inline hooking, plus a few correctness fixes surfaced along the way. Targets Linux, macOS, and Windows on x86-64.

Intention

The Zyrex hook engine needs to allocate executable trampolines near a target (within +/-2 GiB), query existing page protections, and suspend and redirect threads while a patch is applied. Those capabilities previously existed only implicitly on Windows. This adds portable APIs so the hook engine can run on POSIX.

Changes

ZyanMemoryVirtualAlloc and ZyanMemoryVirtualQuery, including an address hint for near allocation within +/-2 GiB of a target.
Thread control: ZyanThreadEnumerate, ZyanThreadSuspend / ZyanThreadResume, and get/set instruction pointer, using a realtime-signal park mechanism on Linux.
Fix ZyanProcessFlushInstructionCache on POSIX to use __builtin___clear_cache instead of msync, which only accepts page-aligned ranges.
Fix ZYAN_ALIGN_DOWN so it no longer misaligns values that are already aligned.
Bound the ZyanThreadSuspend park-wait so it cannot deadlock on a thread that is exiting.