Add string expansion reporting

And fix line counting with expansion-made newlines.
This has the same bug as the old lexer (equs-newline's output does not
print the second warning as being part of the expansion).
Additionally, we regress equs-recursion, as we are no longer able to
catch this specific EQUS recursion. Simply enough, the new expansion
begins **after** the old one ends! I have found no way to handle that.

test/asm/equs-newline.asm

@@ -0,0 +1,4 @@
+
+ACT equs "WARN \"First\"\nWARN \"Second\""
+	ACT
+	WARN "Third"