www: Add link to newly released islplot library

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@198594 91177308-0d34-0410-b5e6-96231b3b80d8
www: Fix typo

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@198595 91177308-0d34-0410-b5e6-96231b3b80d8
www: Fix typo II

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@198596 91177308-0d34-0410-b5e6-96231b3b80d8