Some cleanups for compilation with GCC 4.0.0 to remove warnings:

* Use C++ style casts, not C style casts
* Abstract base classes should have virtual destructor.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22057 91177308-0d34-0410-b5e6-96231b3b80d8

lib/VMCore/AsmWriter.cpp

@@ -34,6 +34,9 @@ using namespace llvm;
 
 namespace llvm {
 
+// Make virtual table appear in this compilation unit.
+AssemblyAnnotationWriter::~AssemblyAnnotationWriter() {}
+
 /// This class provides computation of slot numbers for LLVM Assembly writing.
 /// @brief LLVM Assembly Writing Slot Computation.
 class SlotMachine {