Add a 'deleteModule' method to the Linker class.

This deletes the Module ivar instead of having the LTO code generater do it. It
also sets the pointer to 'NULL', so that if it's used again it will abort
quickly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192778 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Linker.h

@@ -32,7 +32,9 @@ class Linker {
 
     Linker(Module *M);
     ~Linker();
+
     Module *getModule() const { return Composite; }
+    void deleteModule();
 
     /// \brief Link \p Src into the composite. The source is destroyed if
     /// \p Mode is DestroySource and preserved if it is PreserveSource.