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/docs/CommandLine.rst b/llvm/docs/CommandLine.rst
index 9496157..9a6a196 100644
--- a/llvm/docs/CommandLine.rst
+++ b/llvm/docs/CommandLine.rst
@@ -886,12 +886,12 @@
   // debug build, then the code specified as the option to the macro will be
   // executed.  Otherwise it will not be.
   #ifdef NDEBUG
-  #define DEBUG(X)
+  #define LLVM_DEBUG(X)
   #else
-  #define DEBUG(X) do { if (DebugFlag) { X; } } while (0)
+  #define LLVM_DEBUG(X) do { if (DebugFlag) { X; } } while (0)
   #endif
 
-This allows clients to blissfully use the ``DEBUG()`` macro, or the
+This allows clients to blissfully use the ``LLVM_DEBUG()`` macro, or the
 ``DebugFlag`` explicitly if they want to.  Now we just need to be able to set
 the ``DebugFlag`` boolean when the option is set.  To do this, we pass an
 additional argument to our command line argument processor, and we specify where