[Clang] Migrate llvm::make_unique to std::make_unique

Now that we've moved to C++14, we no longer need the llvm::make_unique
implementation from STLExtras.h. This patch is a mechanical replacement
of (hopefully) all the llvm::make_unique instances across the monorepo.

Differential revision: https://reviews.llvm.org/D66259

llvm-svn: 368942
diff --git a/clang/lib/Lex/Pragma.cpp b/clang/lib/Lex/Pragma.cpp
index 4e4db66..8317e99 100644
--- a/clang/lib/Lex/Pragma.cpp
+++ b/clang/lib/Lex/Pragma.cpp
@@ -183,7 +183,7 @@
       assert(!Tokens.empty() && "collected unexpected number of tokens");
 
       // Push the ( "string" ) tokens into the token stream.
-      auto Toks = llvm::make_unique<Token[]>(Tokens.size());
+      auto Toks = std::make_unique<Token[]>(Tokens.size());
       std::copy(Tokens.begin() + 1, Tokens.end(), Toks.get());
       Toks[Tokens.size() - 1] = Tok;
       Self.EnterTokenStream(std::move(Toks), Tokens.size(),