SILOptimizer: use qualified names

Add the missing std:: prefix on the next and prev functions.  These are needed
after LLVM header updates.

Author: compnerd

lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp

@@ -671,7 +671,7 @@ SILCombiner::visitInjectEnumAddrInst(InjectEnumAddrInst *IEAI) {
 
     auto *Term = IEAI->getParent()->getTerminator();
     if (isa<CondBranchInst>(Term) || isa<SwitchValueInst>(Term)) {
-      auto BeforeTerm = prev(prev(IEAI->getParent()->end()));
+      auto BeforeTerm = std::prev(std::prev(IEAI->getParent()->end()));
       auto *SEAI = dyn_cast<SelectEnumAddrInst>(BeforeTerm);
       if (!SEAI)
         return nullptr;

lib/SILOptimizer/Utils/Local.cpp

@@ -1231,7 +1231,7 @@ bool ValueLifetimeAnalysis::computeFrontier(Frontier &Fr, Mode mode) {
       // the last use is part of the frontier.
       SILInstruction *LastUser = findLastUserInBlock(BB);
       if (!isa<TermInst>(LastUser)) {
-        Fr.push_back(&*next(LastUser->getIterator()));
+        Fr.push_back(&*std::next(LastUser->getIterator()));
         continue;
       }
       // In case the last user is a TermInst we add all successor blocks to the