move isl_{pw_,}aff_list functions out of include/isl/aff_type.h
They were moved in together with isl_aff_list and isl_pw_aff_list
themselves in
isl-0.11.2-92-g3e27dfa14 (declare isl_*_list together
with isl_*, Wed Mar 27 12:09:23 2013 +0100), but this sort of defeats
the purpose of
isl-0.06-240-g8b9c16295 (split off declarations
for isl_aff and isl_pw_aff to separate file,
Fri Jul 1 14:38:32 2011 +0200).
Move the function declarations out again, leaving only
the type declarations.
Signed-off-by: Sven Verdoolaege <sven@cerebras.net>