Kudos to jwe on exception handling

[Rik]

All,

I wanted to give a shout out to jwe who has been doing exceptional (pun
intended) work transitioning the core away from using the global variable
error_state.  The implementation began in Darmstadt just 2 weeks ago and if
I grep through libinterp for "error_state" from that time I find 1671
instances.  Today, the number is down to 496.  70% of the instances have
been removed, and most of them it seems in just the last day.  Hip Hip Hurray!

--Rik