Spell `necessary' correctly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7944 91177308-0d34-0410-b5e6-96231b3b80d8

lib/VMCore/Verifier.cpp

@@ -260,7 +260,7 @@ void Verifier::visitReturnInst(ReturnInst &RI) {
             "Function return type does not match operand "
             "type of return inst!", &RI, F->getReturnType());
 
-  // Check to make sure that the return value has neccesary properties for
+  // Check to make sure that the return value has necessary properties for
   // terminators...
   visitTerminatorInst(RI);
 }