adding include unistd.h to srpc_shm.c
adding include unistd.h to srpc_shm.c

TEST=run in chrome.

Review URL: http://codereview.chromium.org/4070001

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@3535 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client