Another step towards getting rid of static ctors for pass registration: have INITIALI...

Another step towards getting rid of static ctors for pass registration: have INITIALIZE_PASS AND INITIALIZE_AG_PASS
expand to an initializeMyPass() function (in additional to the extant static ctors).  Eventually, these will be called
from a big InitializeAllPasses() function, and the PassInfo's they create (which would be leaked if this code were used
at the moment) will be handed off to a PassRegistry for ownership.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115703 91177308-0d34-0410-b5e6-96231b3b80d8