Add a new attribute: norecurse

Add a new attribute: norecurse

This attribute allows the compiler to assume that the function never recurses into itself, either directly or indirectly (transitively). This can be used among other things to demote global variables to locals.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252282 91177308-0d34-0410-b5e6-96231b3b80d8