Replace "fallthrough" comments with LLVM_FALLTHROUGH

This is a mechanical change of comments in switches like fallthrough,
fall-through, or fall-thru to use the LLVM_FALLTHROUGH macro instead.

llvm-svn: 278902
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 7d53b3d..bce0acb 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2700,7 +2700,7 @@
   case InlineAsm::Constraint_i:
     // FIXME: It seems strange that 'i' is needed here since it's supposed to
     //        be an immediate and not a memory constraint.
-    // Fallthrough.
+    LLVM_FALLTHROUGH;
   case InlineAsm::Constraint_o: // offsetable        ??
   case InlineAsm::Constraint_v: // not offsetable    ??
   case InlineAsm::Constraint_m: // memory