Add a doxygen comment to DebugLocEntry::Merge.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205374 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DebugLocEntry.h

@@ -94,6 +94,9 @@ public:
     EntryKind = E_ConstantInt;
   }
 
+  /// \brief Attempt to merge this DebugLocEntry with Next and return
+  /// true if the merge was successful. Entries can be merged if they
+  /// share the same Loc/Constant and their ranges are adjacent.
   bool Merge(const DebugLocEntry &Next) {
     if (End == Next.Begin && hasSameValueOrLocation(Next)) {
       End = Next.End;