v1.6

Add a -v DSUB=... option

It is limilar to SUB but performs substitutions in the original descriptions. For
example, using -v DSUB='$$(DEPS):$(DEPS)', the target

DEPS := x y

Prerequisites: $(DEPS)

t: $(DEPS)

would be documented as:

t Prerequisites: x y

What's Changed

• Add DSUB option by @drdv in #65

Full Changelog: v1.5...v1.6