am c7dc8425: am 42ac0e50: Merge "Revert "libc: Provide ucontext_t/mcontext_t/<sys/ucontext.h>""

* commit 'c7dc842529ea6f8801164eb8b4f7d036acc53955':
  Revert "libc: Provide ucontext_t/mcontext_t/<sys/ucontext.h>"