Disable most IR-level transform passes on functions marked 'optnone'.

Disable most IR-level transform passes on functions marked 'optnone'.
Ideally only those transform passes that run at -O0 remain enabled,
in reality we get as close as we reasonably can.
Passes are responsible for disabling themselves, it's not the job of
the pass manager to do it for them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200892 91177308-0d34-0410-b5e6-96231b3b80d8