isl_printer_print_union_access_info: extract out field names
isl_printer_print_union_access_info: extract out field names

This will allow the names to be reused for parsing isl_union_access_info
objects.

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

tobig/isl,nicolasvasilache/isl,Meinersbur/isl,Meinersbur/isl,inducer/isl-mirror,PollyLabs/isl,tobig/isl,nicolasvasilache/isl,inducer/isl-mirror,PollyLabs/isl,inducer/isl-mirror,inducer/isl-mirror,tobig/isl,tobig/isl,PollyLabs/isl,inducer/isl-mirror,Meinersbur/isl,nicolasvasilache/isl,nicolasvasilache/isl,PollyLabs/isl,nicolasvasilache/isl,Meinersbur/isl,PollyLabs/isl