Implement spawn.h + fix VaList API for Rust 1.98 + signal.h stdint.h
spawn.h: Implement posix_spawn/posix_spawnp with file actions and
spawn attributes (flags, pgroup, sigmask, sigdefault). Uses fork+exec.
signal/cbindgen.toml: Add stdint.h to sys_includes for signalfd_siginfo
fixed-width integer types (uint32_t, int32_t, etc.).
VaList API migration for Rust 1.98.0-dev toolchain:
- VaListImpl merged into VaList (core::ffi::VaList)
- .arg()/.arg::<T>() renamed to .next_arg()/.next_arg::<T>()
- .as_va_list() removed (parameter is already VaList)
- .with_copy() replaced with .clone()
- printf.rs: Fix double-dereference cast for inline VaListInner
redox-rt/signal.rs: Remove unnecessary unsafe around __cpuid (safe in
new nightly).
Red Bear OS
ae6549251b