Preselection is _not_ a basicblock pass, because it adds global variables to

Preselection is _not_ a basicblock pass, because it adds global variables to
the module.  This change converts it from being a basic block pass to being
a simple pass.  This allows elimination of the annotation and simplification
of the logic for moving constants into global variables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9320 91177308-0d34-0410-b5e6-96231b3b80d8