[Sema] Replace mem_fn with lambdas. NFC.

I'm told that some optimizers like lambdas a lot more than mem_fn.
Given that the readability difference is basically nil, and we seem to
use lambdas basically everywhere else, it seems sensible to just use
lambdas.

llvm-svn: 276577
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index dfb4cce..090fab7 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -39,8 +39,9 @@
 using namespace sema;
 
 static bool functionHasPassObjectSizeParams(const FunctionDecl *FD) {
-  return llvm::any_of(FD->parameters(),
-                      std::mem_fn(&ParmVarDecl::hasAttr<PassObjectSizeAttr>));
+  return llvm::any_of(FD->parameters(), [](const ParmVarDecl *P) {
+    return P->hasAttr<PassObjectSizeAttr>();
+  });
 }
 
 /// A convenience routine for creating a decayed reference to a function.
@@ -8954,8 +8955,9 @@
     return false;
   }
 
-  auto I = llvm::find_if(
-      FD->parameters(), std::mem_fn(&ParmVarDecl::hasAttr<PassObjectSizeAttr>));
+  auto I = llvm::find_if(FD->parameters(), [](const ParmVarDecl *P) {
+    return P->hasAttr<PassObjectSizeAttr>();
+  });
   if (I == FD->param_end())
     return true;