JPSSnagg

test/testnagg.sh:
    Previous tests only check exit code.  Improve testing by adding two new
    features to testnagg.sh that will verify the expoected output for some
    tests:
    CHECK_OUTPUT:
	run the tool test and expect succeed (exit code 0) with expected output
    CHECK_FAIL_OUTPUT:
	run the tool test and expect failure (exit code 1) with expected output

    Current expected output verification can handle fixed output only. Next
    improvement is to verify time-dependent (e.g., the creation time in the
    output file names.)

test/testfiles/usage.txt:
    Expected output of the help option.
src/nagg_options.c:
    removed a typo.

Tested: jam and koala