Test that OPT r fails immediately if the recursion depth is already exceeded

Fixes #1034

test/asm/opt-r-decrease.asm

@@ -0,0 +1,11 @@
+MACRO m
+  DEF depth += 1
+  IF depth == 10
+    OPT r9
+  ENDC
+  println "at depth {d:depth}"
+  m
+ENDM
+
+  DEF depth = 0
+  m