better error when trying to check-updates without src/
Add 'make check' as a synomym for 'make test'.

This is what they call it where I come from.
Merge pull request #2 from rillian/fixes

add `make check` as alias for `make test`

That's the GNU way, people seem to care and it's not intrusive, so why not.
https://www.gnu.org/prep/standards/standards.html#Standard-Targets
be consistant with target ordering. check is before test, so reflect that in .PHONY