Upgrade compat.h and compat-inl.h.

Upgrade the v0.10/v0.11/v0.12 compatibility shim to the latest version
from strongloop/strong-agent.  Motivation: it has utility methods for
raising exceptions.
Remove homegrown ThrowException shim.

Replace the ThrowException() helper with the ThrowError() method from
compat.h.

Fixes #2.