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

The patch is generated using this command:

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

To reduce churn, not touching namespaces spanning less than 10 lines.

llvm-svn: 240270
diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
index 8165b09..795d674 100644
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -370,7 +370,7 @@
                         const Stmt *S,
                         clang::reachable_code::Callback &CB);
   };
-}
+} // namespace
 
 void DeadCodeScan::enqueue(const CFGBlock *block) {
   unsigned blockID = block->getBlockID();
@@ -676,4 +676,5 @@
   }
 }
 
-}} // end namespace clang::reachable_code
+} // namespace reachable_code
+} // namespace clang