[WebAssemby] Implement block signatures.

Per spec changes, this implements block signatures, and adds just enough
logic to produce correct block signatures at the ends of functions.

Differential Revision: https://reviews.llvm.org/D25144

llvm-svn: 283503
diff --git a/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.h b/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.h
index 07b0f91..d11f99c 100644
--- a/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.h
+++ b/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.h
@@ -39,6 +39,8 @@
   void printOperand(const MCInst *MI, unsigned OpNo, raw_ostream &O);
   void printWebAssemblyP2AlignOperand(const MCInst *MI, unsigned OpNo,
                                       raw_ostream &O);
+  void printWebAssemblySignatureOperand(const MCInst *MI, unsigned OpNo,
+                                        raw_ostream &O);
 
   // Autogenerated by tblgen.
   void printInstruction(const MCInst *MI, raw_ostream &O);