[PATCH] gcc parallel make check

[VandeVondele Joost]

> So, I’d love to see the numbers for 5 and 20 to double check that 10 is the right number to pick.  This sort of refinement is trivial post checkin.

So, some timings with the patch, I think this is great. 

Doing the testing you suggest, changing the variable doesn't influence things much (at least for Fortran, and  on this system).

make -j32 -k
check-fortran
real    3m27.875s -> gcc_runtest_parallelize_counter_minor == 02 (several testsuite errors: binding_label_tests_10_main.f03, binding_label_tests_11_main.f03, class_45b.f03, class_4b.f03, class_4c.f03, coarray_29_2.f90, test_common_binding_labels_3_main.f03)
real    3m26.234s -> gcc_runtest_parallelize_counter_minor == 05 (one additional testsuite error: whole_file_31.f90)
real    3m36.405s -> gcc_runtest_parallelize_counter_minor == 10
real    3m38.736s -> gcc_runtest_parallelize_counter_minor == 20
check-c
real    8m26.935s
check-c++
real    7m4.165s
check
real   17m45.185s