Add missing headers

These headers are needed for pid_t and free when using libc++ headers (POSIX
does not require that the symbols be exposed with the previous includes).

(cherry picked from commit ac2fe7eb81789274ab98573d0c4b0866bed1f254)

Change-Id: I3b3635c8f446f1ca0c20a23d63d77587c2dffc16
2 files changed