Change std::{lower,upper}_bound to llvm::{lower,upper}_bound or llvm::partition_point. NFC

llvm-svn: 365006
diff --git a/clang/lib/Basic/DiagnosticIDs.cpp b/clang/lib/Basic/DiagnosticIDs.cpp
index e8a99d0..f189e5d 100644
--- a/clang/lib/Basic/DiagnosticIDs.cpp
+++ b/clang/lib/Basic/DiagnosticIDs.cpp
@@ -580,11 +580,8 @@
 bool
 DiagnosticIDs::getDiagnosticsInGroup(diag::Flavor Flavor, StringRef Group,
                                      SmallVectorImpl<diag::kind> &Diags) const {
-  auto Found = std::lower_bound(std::begin(OptionTable), std::end(OptionTable),
-                                Group,
-                                [](const WarningOption &LHS, StringRef RHS) {
-                                  return LHS.getName() < RHS;
-                                });
+  auto Found = llvm::partition_point(
+      OptionTable, [=](const WarningOption &O) { return O.getName() < Group; });
   if (Found == std::end(OptionTable) || Found->getName() != Group)
     return true; // Option not found.