Replace atomic_increment and atomic_increment_val with atomic_fetch_add_relaxed.
One case in sem_post.c uses release semantics (see comment above it).
The others are simple counters and do not protect any shared data from
concurrent accesses.
Passes regress on AArch64.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This patch adds a new "Inter-Process Communication"
chapter to cover the sem*, msg*, and shm* functions.
Initially we document only the sem* function signatures
and their safety notes.
