Switch over to the parallelized makefile, but keep old serial

makefile around (just change Makefile.parallel to Makefile to
get back old functionality).

To run parallel tests, specify

    make -jN test # where N = num of CPUs * 2

to get detailed output, run

    make -jN test VERBOSE=1

to only get error descriptions *after the tests have run*, type

    make report

this gives you the extra information which was omitted in non-VERBOSE
mode.

llvm-svn: 48486