Rename DEBUG macro to LLVM_DEBUG.
    
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.

In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.

Differential Revision: https://reviews.llvm.org/D43624

llvm-svn: 332240
diff --git a/llvm/lib/Target/Lanai/LanaiISelLowering.cpp b/llvm/lib/Target/Lanai/LanaiISelLowering.cpp
index 3345513..22fcf47 100644
--- a/llvm/lib/Target/Lanai/LanaiISelLowering.cpp
+++ b/llvm/lib/Target/Lanai/LanaiISelLowering.cpp
@@ -484,8 +484,8 @@
         break;
       }
       default:
-        DEBUG(dbgs() << "LowerFormalArguments Unhandled argument type: "
-                     << RegVT.getEVTString() << "\n");
+        LLVM_DEBUG(dbgs() << "LowerFormalArguments Unhandled argument type: "
+                          << RegVT.getEVTString() << "\n");
         llvm_unreachable("unhandled argument type");
       }
     } else {