Allow changing recursion depth limit at runtime

test/asm/opt-r.asm

@@ -0,0 +1,13 @@
+OPT r34 ; :3
+OPT r 360
+
+; Invalid
+OPT r ; Missing arg
+OPT r 2a ; Bad decimal
+
+; Check that it has an effect
+OPT r 1
+MACRO m
+	m
+ENDM
+	m

test/asm/opt-r.err

@@ -0,0 +1,6 @@
+error: opt-r.asm(5):
+    Missing argument to option 'r'
+error: opt-r.asm(6):
+    Invalid argument to option 'r' ("2a")
+FATAL: opt-r.asm(13):
+    Recursion limit (1) exceeded