sim: example-synacor: a simple implementation for reference

Provide a simple example simulator for people porting to new targets
to use as a reference.  This one has the advantage of being used by
people and having a fun program available for it.

It doesn't require a special target -- the example simulators can be
built for any existing port.

sim/testsuite/example-synacor/mod.s

@@ -0,0 +1,18 @@
+# check the MOD insn.
+# mach: example
+
+.include "testutils.inc"
+
+	start
+	JMP 3
+	HALT
+
+	MOD r0, 8, 3
+	EQ r1, r0, 2
+	JF r1, 2
+
+	MOD r0, r0, 2
+	EQ r1, r0, 0
+	JF r1, 2
+
+	pass