generator::generator.cc: drop spurious declaration
generator::generator.cc: drop spurious declaration

The declaration was introduced by isl-0.18-595-gdab674e14c (Turn python
generator into a subclass of generator, Sat Apr 8 05:12:47 2017 +0200).

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

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