switch instructions only allow constantints for their values, be more specific.

llvm-svn: 20298
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index 73183a3..bc1bfcc 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -948,7 +948,7 @@
 
 /// addCase - Add an entry to the switch instruction...
 ///
-void SwitchInst::addCase(Constant *OnVal, BasicBlock *Dest) {
+void SwitchInst::addCase(ConstantInt *OnVal, BasicBlock *Dest) {
   unsigned OpNo = NumOperands;
   if (OpNo+2 > ReservedSpace)
     resizeOperands(0);  // Get more space!