Correct logic around exporting and using external parsers.
Correct logic around exporting and using external parsers.

Leaving this macro-glue untouched just happens to work for the mix used
buy the passwd and group types but breaks for others that I am adding.
Replace the existing logic only do 'static' or 'extern' but nothing in
between.

aperezdc/nss-altfiles,aperezdc/nss-altfiles,coreos/nss-altfiles,coreos/nss-altfiles