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.

llvm-svn: 199582

Author: tobiasgrosser

polly/utils/checkout_cloog.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 
-CLOOG_HASH="88986e94581bece13c77d51ab18c7b20da14fb67"
-ISL_HASH="34eb3a0c3d52875ec93e926f12713feff4d08af0"
+CLOOG_HASH="2d8b7c6b43ee46fee978a57fa6877de49675f357"
+ISL_HASH="1b3ba3b72c0482fd36bf0b4a1186a259f7bafeed"
 
 PWD=`pwd`