Introduce extension '.run' for tests and use it consistently.

.gitignore

configure.ac

tests/Makefile.am

tests/pio_cksum_asynch.run.in

tests/pio_cksum_fpguard.run.in

tests/pio_cksum_grb2.run.in

tests/pio_cksum_mpi_fw_at_all.run.in

tests/pio_cksum_mpi_fw_at_reblock.run.in

tests/pio_cksum_mpi_fw_ordered.run.in

tests/pio_cksum_mpinonb.run.in

tests/pio_cksum_nc.run.in

tests/pio_cksum_nc2.run.in

tests/pio_cksum_nc4.run.in

tests/pio_cksum_writer.run.in

tests/pio_write.parallel.run.in

tests/pio_write.run.in

tests/pio_write_deco2d.parallel.run.in

tests/pio_write_deco2d.run.in

tests/pio_write_dist_array.run.in

tests/test_cdf_const.run.in