Remove unnecessary overhead in execunix.c related to
the timeout implementation. Also removed unused variables
as diagnosed by the Sgi (mipspro) compiler.
Fixed const-correctness error in operations.hpp that
Sgi complained about.
There's no strerror_r function on Irix 6.5 so I replaced
it with a strerror call.
With these changes, I can now build process jam log and
start running Sgi tests.