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/CodeGen/MachineFrameInfo.cpp b/llvm/lib/CodeGen/MachineFrameInfo.cpp
index d0c737b..0b31687 100644
--- a/llvm/lib/CodeGen/MachineFrameInfo.cpp
+++ b/llvm/lib/CodeGen/MachineFrameInfo.cpp
@@ -41,9 +41,9 @@
                                            unsigned StackAlign) {
   if (!ShouldClamp || Align <= StackAlign)
     return Align;
-  DEBUG(dbgs() << "Warning: requested alignment " << Align
-               << " exceeds the stack alignment " << StackAlign
-               << " when stack realignment is off" << '\n');
+  LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Align
+                    << " exceeds the stack alignment " << StackAlign
+                    << " when stack realignment is off" << '\n');
   return StackAlign;
 }