Fix sed tests so that they run cleanly with prove.
Fix yacc tests so that they run cleanly with prove.

First, change the driver to run the installed yacc instead of the one from
/usr/obj (which might not be there), just as we (intend to) do with all
other tests.

Second, regenerate the expected output files from scratch.  Based on visual
inspection, the differences seem OK.  But this highlights that the tests in
here are too fragile and, possibly, useless: we should be testing the
behavior of the generated program, not the literal output.  Something to be
addressed later.
Fix pkill tests so that they run cleanly with prove.

This fixes a pgrep test that assumed that PID 2 was named g_event.  This
does not seem to be the case any longer (and I don't know if it ever was
in all possible setups).

Change this test to use the idle loop instead and determine its expected
PID using ps without assuming any specific ID.
Fix ncal tests so that they run cleanly with prove.

Basically just make the test plan match what is actually being run.