[LLDB] 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: 368933
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index 4eac3ab..6e1c90a 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -8444,7 +8444,7 @@
   if (!type)
     return nullptr;
 
-  return llvm::make_unique<clang::CXXBaseSpecifier>(
+  return std::make_unique<clang::CXXBaseSpecifier>(
       clang::SourceRange(), is_virtual, base_of_class,
       ClangASTContext::ConvertAccessTypeToAccessSpecifier(access),
       getASTContext()->getTrivialTypeSourceInfo(GetQualType(type)),