Fixing modular build issues caused by BitCodes.h

[kristina]

Summary

Consolidate llvm::BWH_* statics into an enum to fix module build issues. This fixes the LLVM_Bitcode module (getting rid of -Wmodules-ambiguous-internal-linkage).

[thegameg]

LGTM, thanks! Sorry for the breakage!

llvm/trunk/include/llvm/Bitstream/BitCodes.h

 
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <cassert>
 
 namespace llvm {
 /// Offsets of the 32-bit fields of bitstream wrapper header.
-static const unsigned BWH_MagicField = 0 * 4;
-static const unsigned BWH_VersionField = 1 * 4;
-static const unsigned BWH_OffsetField = 2 * 4;
-static const unsigned BWH_SizeField = 3 * 4;
-static const unsigned BWH_CPUTypeField = 4 * 4;
-static const unsigned BWH_HeaderSize = 5 * 4;
+enum BitstreamWrapperHeader : unsigned {
+  BWH_MagicField   = 0 * 4,
+  BWH_VersionField = 1 * 4,
+  BWH_OffsetField  = 2 * 4,
+  BWH_SizeField    = 3 * 4,
+  BWH_CPUTypeField = 4 * 4,
+  BWH_HeaderSize   = 5 * 4
+};
 
 namespace bitc {
   enum StandardWidths {
     BlockIDWidth   = 8,  // We use VBR-8 for block IDs.
     CodeLenWidth   = 4,  // Codelen are VBR-4.
     BlockSizeWidth = 32  // BlockSize up to 2^32 32-bit words = 16GB per block.
   };