Direct, unsafe Rust bindings for Linux's perf_event_open system call

This crate exports unsafe Rust wrappers for Linux system calls for accessing performance monitoring counters and tracing facilities. This includes:

• the processor's own performance monitoring registers
• kernel counters for things like context switches and page faults
• kernel tracepoints, kprobe, and uprobes
• processor tracing facilities like Intel's Branch Trace Store (BTS)
• hardware breakpoints

This crate provides:

• a Rust wrapper the Linux perf_event_open system call
• Rust wrappers for the ioctls you can apply to a file descriptor returned by perf_event_open
• bindings for perf_event_open's associated header files, automatically generated by bindgen

All functions are direct, unsafe wrappers for the underlying calls. They operate on raw pointers and raw file descriptors.