Update to the latest cloog and isl versions

This brings in isl_val support from cloog and, most importantly the following
isl commit:

commit d962967ab42323ea5ca0398956fbff6a98c782fa
Author: Sven Verdoolaege <skimo@kotnet.org>
Date:   Wed Dec 18 12:05:32 2013 +0100

    allow the user to impose a bound on the number of low-level operations

    This should allow the user to deterministically limit the effort spent on a
    computation.
[CMake] Import CLANG_TOOLS_DIR from check-clang into check-clang-tools for standalone clang.
CodeGeneration: Replace reference to isl_int with explicit mpz call.

This removes the last isl_int dependency in the default build. There are
still some in OpenScop and Scoplib. For those isl-0.12.2 still needs to be used.