IPSCCP apparently is not a superset of IPCP, this is bad,

but I'll investigate it separately.  This unbreaks 
test/FrontendC/weak_constant.c


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85735 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/StandardPasses.h

@@ -100,6 +100,7 @@ namespace llvm {
     if (UnitAtATime) {
       PM->add(createGlobalOptimizerPass());     // Optimize out global vars
       
+      PM->add(createIPConstantPropagationPass());              // IP CP
       PM->add(createIPSCCPPass());              // IP SCCP
       PM->add(createDeadArgEliminationPass());  // Dead argument elimination
     }