Merge pull request #11 from gerdr/master

Makefile fix
New Makefile with mostly atomic rules suitable for parallel make
Fix nqp::substr; patch from nwc10++.
Implement and test existspos
Merge pull request #13 from tadzik/existspos

Implement and test existspos
Merge pull request #12 from gerdr/newmakefile

New Makefile with mostly atomic rules suitable for parallel make