extract_interface.cc: extract out generate function
extract_interface.cc: extract out generate function

This will make it easier to add support for additional languages.

Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

PollyLabs/isl,PollyLabs/isl,PollyLabs/isl,Meinersbur/isl,PollyLabs/isl,Meinersbur/isl,Meinersbur/isl,PollyLabs/isl,Meinersbur/isl