Clean up tests

tests/.gitignore

tests/Makefile

tests/expected/exec.stdout

tests/expected/fcntl/create.stderr

tests/expected/fcntl/create.stdout

tests/expected/fcntl/fcntl.stderr

tests/expected/fcntl/fcntl.stdout

tests/expected/stdio/getc_unget.stderr

tests/expected/stdio/getc_unget.stdout

tests/expected/stdio/printf.stderr

tests/expected/stdio/printf.stdout

tests/expected/stdio/rename.stderr

tests/expected/stdio/rename.stdout

tests/expected/stdio/scanf.stderr

tests/expected/stdio/scanf.stdout

tests/expected/stdio/sprintf.stderr

tests/expected/stdio/sprintf.stdout

tests/expected/stdlib/atof.stderr

tests/expected/stdlib/atof.stdout

tests/expected/stdlib/atoi.stderr