Another paralell make patch for libf2c

[Dave Love]

>>>>> "HJ" == H J Lu <hjl@lucon.org> writes:

 HJ> If it takes more than 5 minutes to see why this patch is needed,
 HJ> you need to read the GNU make manual again.

Oh come on!  Even if that's true (which I doubt), if we all waste 5
minutes of Jeff's time a day, where will that leave us?

It isn't obvious to me -- who's fault any bug or lack of documentation
there presumably is -- that the patch is the right thing, but I
haven't had a chance to take a proper look yet.  I'm sorry to take
_any_ of Jeff's time as a result.

The last such change (without explanation AFAIR) appeared not to be
appropriate and I made a different one, approved by Craig.  To
convince us that was wrong will take more than proof by assertion.