Make __has_feature(nullability) and __has_extension(nullability) always true.

These are _Underbar_capital-prefixed additions to the language that
shouldn't depend on language standard.

llvm-svn: 240976
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 3855c80..d52519e 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1052,7 +1052,7 @@
       .Case("address_sanitizer",
             LangOpts.Sanitize.hasOneOf(SanitizerKind::Address |
                                        SanitizerKind::KernelAddress))
-      .Case("assume_nonnull", LangOpts.ObjC1 || LangOpts.GNUMode)
+      .Case("assume_nonnull", true)
       .Case("attribute_analyzer_noreturn", true)
       .Case("attribute_availability", true)
       .Case("attribute_availability_with_message", true)
@@ -1077,7 +1077,7 @@
       .Case("cxx_exceptions", LangOpts.CXXExceptions)
       .Case("cxx_rtti", LangOpts.RTTI)
       .Case("enumerator_attributes", true)
-      .Case("nullability", LangOpts.ObjC1 || LangOpts.GNUMode)
+      .Case("nullability", true)
       .Case("memory_sanitizer", LangOpts.Sanitize.has(SanitizerKind::Memory))
       .Case("thread_sanitizer", LangOpts.Sanitize.has(SanitizerKind::Thread))
       .Case("dataflow_sanitizer", LangOpts.Sanitize.has(SanitizerKind::DataFlow))
@@ -1226,8 +1226,6 @@
   // Because we inherit the feature list from HasFeature, this string switch
   // must be less restrictive than HasFeature's.
   return llvm::StringSwitch<bool>(Extension)
-           .Case("assume_nonnull", true)
-           .Case("nullability", true)
            // C11 features supported by other languages as extensions.
            .Case("c_alignas", true)
            .Case("c_alignof", true)