Log Message:
Drop support for TOOLS_DEPMETHOD.<tool>.  The new way to specify a
run-time dependency (DEPENDS) on a tool is to append a ":run" modifier
to the tool name, e.g.,

	USE_TOOLS+=	perl:run

Tools without modifiers or with an explicit ":build" modifier will
cause build dependencies (BUILD_DEPENDS) on those tools to be added.
This makes the notation a bit more compact.