isl_ast_build_expr.c: isl_ast_build_from_multi_pw_aff: use isl_bool
isl_ast_build_expr.c: isl_ast_build_from_multi_pw_aff: use isl_bool

This was missing from isl-0.14.1-479-g370a8b7d0 (introduce isl_bool and
isl_stat return types, Mon May 4 09:45:16 2015 +0200).

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

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