[J-core] Sega saturn retrocomputing.

[Rob Landley]

FYI:

http://hackaday.com/2016/07/11/cracking-the-sega-saturn-after-20-years/

(Alas, when we looked at possibly doing an FPGA saturn clone with J2 as
a side project for the 20th anniversary, it turned out there were some
tight timing constraints that make games misbehave very easily, at least
in software emulation. I think some j2 instructions take different
numbers of clock cycles than sh2 did? Don't remember the details, but we
shelved the idea...)

Rob