Grrr, make the test for embedded variables in the left-hand-side actually do
the right thing in every case. Yuck.

Add a test for what was fixed in revision 1.27 and 1.28 of make(1)'s var.c,
expansion of embedded variables in the left-hand-side of an assignment
expression, using the simplest case - hiding recursi

Add a test for what was fixed in revision 1.27 and 1.28 of make(1)'s var.c,
expansion of embedded variables in the left-hand-side of an assignment
expression, using the simplest case - hiding recursion using nil-expanded
variables.

show more ...

Add a regression test for bin/5297, regarding sysv substitution with a nil
left-hand-side.

Prefix tests with PASS and FAIL, to make grepping easier, and note this in
the README.

This affects only the base-system regression tests, of course.

Check to see if make(1)'s handling of doubly-defined targets is busted or
not. A lot relies on this.

Add a test of variable evaluation and substitution for make(1), as a start
of tests for it.