Make AsmPrinter::EmitJumpTableInfo virtual

[sunfish]

Summary

Targets that have non-traditional jump table mechanisms may need to do something substantially different for jump tables than what AsmPrinter::EmitJumpTableInfo does. This patch makes that function virtual so that targets can override it.

[sunfish]

This patch is depended on by http://reviews.llvm.org/D12787 .

[jfb]

lgtm

llvm/trunk/include/llvm/CodeGen/AsmPrinter.h

public:
   /// constants in the constant pool MCP. This is used to print out constants
   /// which have been "spilled to memory" by the code generator.
   ///
   virtual void EmitConstantPool();
 
   /// Print assembly representations of the jump tables used by the current
   /// function to the current output stream.
   ///
-  void EmitJumpTableInfo();
+  virtual void EmitJumpTableInfo();
 
   /// Emit the control variable for an emulated TLS variable.
   virtual void EmitEmulatedTLSControlVariable(const GlobalVariable *GV,
                                               MCSymbol *EmittedSym,
                                               bool AllZeroInitValue);
 
   /// Emit the specified global variable to the .s file.
   virtual void EmitGlobalVariable(const GlobalVariable *GV);