convert PackMachPPC32 to new Linker

src/p_mach.h

@@ -191,6 +191,8 @@ protected:
         upx_byte const *const fold,
         unsigned        const szfold,
         Filter const *ft );
+    virtual void addLinkerSymbols(Filter const *);
+    virtual void addStubEntrySections(Filter const *);
 
     unsigned  n_segment;
     unsigned sz_segment;