Log Message:
Update to 0.13:

version: 0.13
date: Mon Apr 14 11:08:45 CEST 2014
changes:
	- deprecate isl_int
	- improved support for multi piecewise quasi-affine expressions
	- allow the user to impose a bound on the number of low-level operations
	- add isl_id_to_ast_expr and isl_id_to_pw_aff
	- add isl_schedule_constraints
	- hide internal structure of isl_vec
	- remove support for piplib