Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
  -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
  llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137
diff --git a/llvm/lib/Support/Allocator.cpp b/llvm/lib/Support/Allocator.cpp
index f48edac..021037a 100644
--- a/llvm/lib/Support/Allocator.cpp
+++ b/llvm/lib/Support/Allocator.cpp
@@ -37,4 +37,4 @@
          << "Number of elements free for recycling: " << FreeListSize << '\n';
 }
 
-}
+} // namespace llvm