Increase the number of pthread keys available to the IRT
Increase the number of pthread keys available to the IRT

The Mojo EDK uses an additional key for thread-local storage
and is now necessary to bring up IPC in Chrome. This is apparently
enough to push us over the 16 key limit in some cases.

Doubling to 32 to leave some room for further expansion.

BUG=https://code.google.com/p/chromium/issues/detail?id=612500

Review-Url: https://codereview.chromium.org/2050043004

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client