Changes to retrieve test file dir in FileParser from makefile var TEST_FILE_DIR.
Fix a comment typo.
Fix TESTS_ENVIRONMENT order.

VALGRIND_ENVIROMENT has the first part of the valgrind invocation,
assuming automake will append the name of the unittest executable.
We therefore need to place any shell variable assignments before
the valgrind invocation to avoid the shell passing them as arguments
instead of environment variables.