absorb: 27 orphaned relibc patches re-applied (Phase 1.0A)

Per local/docs/PATCH-PRESERVATION-AUDIT-2026-07-12.md the relibc
fork was carrying only 34 of 90 patches in local/patches/relibc/.
The other 56 patches' content was silently missing from the fork.

This commit re-applies 27 patches that genuinely still apply
cleanly. Recovery covers:

- eventfd implementation (sys/eventfd.h + eventfd.rs)
- signalfd implementation (sys/signalfd.h + signalfd.rs)
- timerfd implementation (sys/timerfd.h + timerfd.rs)
- bits/eventfd.h header
- spawn() function: cbindgen + stdint fix
- P3-timerfd-cbindgen-fix
- cbindgen language=C fixes for sys/{timerfd,semaphore}
- stdint include chain fixes
- strtold implementation
- dns aaaa getaddrinfo ipv6
- various stack/threading/header threading fixes
- dup3 syscalls
- waitid implementation
- bits/timespec reverse_from
- open_memstream integration

24 files changed.

redox-rt/src/arch/x86_64.rs

@@ -21,7 +21,7 @@ use super::ForkScratchpad;
 
 // Setup a stack starting from the very end of the address space, and then growing downwards.
 pub const STACK_TOP: usize = 1 << 47;
-pub const STACK_SIZE: usize = 1024 * 1024;
+pub const STACK_SIZE: usize = 8 * 1024 * 1024;
 
 #[derive(Debug, Default)]
 #[repr(C)]