Put Target definitions inside Target specific header, and llvm namespace.

llvm-svn: 76344
diff --git a/llvm/lib/Target/Alpha/Alpha.h b/llvm/lib/Target/Alpha/Alpha.h
index 9226a55..93c4c70 100644
--- a/llvm/lib/Target/Alpha/Alpha.h
+++ b/llvm/lib/Target/Alpha/Alpha.h
@@ -39,6 +39,8 @@
   FunctionPass *createAlphaLLRPPass(AlphaTargetMachine &tm);
   FunctionPass *createAlphaBranchSelectionPass();
 
+  extern Target TheAlphaTarget;
+
 } // end namespace llvm;
 
 // Defines symbolic names for Alpha registers.  This defines a mapping from