Enhance the reduce-depends.awk script to reduce a larger set of
dependencies into a single dependency.  The patterns representing
intervals of version numbers (can be open-ended) are of the form:

	pkg>lower
	pkg>=lower
	pkg<upper
	pkg<=upper
	pkg>lower<upper
	pkg>lower<=upper
	pkg>=lower<upper
	pkg>=lower<=upper

These patterns are now condensed into a single dependency of the
same form.  For example, given the following patterns:

	pkg>=1.0
	pkg>2.0
	pkg<3.0
	pkg<=4.0
	pkg>=2.5<3.5

the reduced pattern becomes:

	pkg>=2.5<3.0

Add the test script used to help with refactoring and adding the
new feature to the script.

This is a mostly complete rewrite of the script; change the
license to the standard 2-clause BSD license used by TNF.

Restore feature from the old script by preserving the order of the
dependencies with respect to their package directories.  This is
important because the buildlink framework causes dependency lists
emitted to have the property where each package of the list only
depends on packages listed before it.

The pkg_info(1) manpage says that underscore (_) is valid and is
equivalent to a period (.) in a version string.