Switch LLVM_USE_RVALUE_REFERENCES to LLVM_HAS_RVALUE_REFERENCES.

Rationale:
1) This was the name in the comment block. ;]
2) It matches Clang's __has_feature naming convention.
3) It matches other compiler-feature-test conventions.

Sorry for the noise. =]

I've also switch the comment block to use a \brief tag and not duplicate
the name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168996 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/LocaleWindows.inc b/lib/Support/LocaleWindows.inc
index 6827ac1..28e429c 100644
--- a/lib/Support/LocaleWindows.inc
+++ b/lib/Support/LocaleWindows.inc
@@ -12,4 +12,4 @@
 
 }
 }
-}
\ No newline at end of file
+}
diff --git a/lib/Support/Unix/PathV2.inc b/lib/Support/Unix/PathV2.inc
index 05fd924..4532670 100644
--- a/lib/Support/Unix/PathV2.inc
+++ b/lib/Support/Unix/PathV2.inc
@@ -546,7 +546,7 @@
     ::munmap(Mapping, Size);
 }
 
-#if LLVM_USE_RVALUE_REFERENCES
+#if LLVM_HAS_RVALUE_REFERENCES
 mapped_file_region::mapped_file_region(mapped_file_region &&other)
   : Mode(other.Mode), Size(other.Size), Mapping(other.Mapping) {
   other.Mapping = 0;
diff --git a/lib/Support/Windows/PathV2.inc b/lib/Support/Windows/PathV2.inc
index 3dfac66..c7ef827 100644
--- a/lib/Support/Windows/PathV2.inc
+++ b/lib/Support/Windows/PathV2.inc
@@ -861,7 +861,7 @@
     ::CloseHandle(FileHandle);
 }
 
-#if LLVM_USE_RVALUE_REFERENCES
+#if LLVM_HAS_RVALUE_REFERENCES
 mapped_file_region::mapped_file_region(mapped_file_region &&other)
   : Mode(other.Mode)
   , Size(other.Size)