Rename llvm::Optional<T>::Reset to 'reset' as per LLVM naming conventions.

Code review feedback on r175580 from Jordan Rose.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175595 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/ADT/OptionalTest.cpp b/unittests/ADT/OptionalTest.cpp
index 8bdea45..6fd8bba 100644
--- a/unittests/ADT/OptionalTest.cpp
+++ b/unittests/ADT/OptionalTest.cpp
@@ -56,7 +56,7 @@
   EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
   EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
   NonDefaultConstructible::ResetCounts();
-  O.Reset();
+  O.reset();
   EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
   EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
   EXPECT_EQ(1u, NonDefaultConstructible::Destructions);