Add an MACOS_VERSION_UNKNOWN_NEWER enum value for OS X versions above 10.10.

We recently had a broken version check because an newer OS X version is treated as MACOS_VERSION_UNKNOWN which is less than all the defined values. Let's have a separate enum value for unknown but newer versions, so the ">=" and "<=" version checks still work even in upcoming OS X releases.

Reviewed at http://reviews.llvm.org/D6137

llvm-svn: 224315
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
index 98c5b94..3c95cba 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
@@ -298,7 +298,11 @@
         case '2': return MACOS_VERSION_MOUNTAIN_LION;
         case '3': return MACOS_VERSION_MAVERICKS;
         case '4': return MACOS_VERSION_YOSEMITE;
-        default: return MACOS_VERSION_UNKNOWN;
+        default:
+          if (IsDigit(version[1]))
+            return MACOS_VERSION_UNKNOWN_NEWER;
+          else
+            return MACOS_VERSION_UNKNOWN;
       }
     }
     default: return MACOS_VERSION_UNKNOWN;