Bump python3 to 3.4.2 to fix build on Mac OS X 10.10

All the C modules were failing with missing symbols on 10.10
(ok on 10.9), causing later builds relying on python modules
to fail.

Bumping up to 3.4.2 from 3.3.5 seems to fix the build on 10.10,
but there might be more that needs to be done to the recipe file.