parallel make

[John Cremona <john.cremona@gmail.com>]

I normally build much faster using "make -j" instead of plain "make".
Now I was just trying "./Configure --tune" for the first time, and I
see that it is doing a full build (and I expect it will do this more
than once given the estimated time for this given in the manual).

If the Makefiles used $MAKE instead of make, then this could also be
sped up via the user setting (e.g.) export MAKE='make -j' before
starting.  Is there any reason why this would not work?

John