Resolve -Wsuggest-override warnings.

include/wx/unix/private/pipestream.h

@@ -21,7 +21,7 @@ public:
     bool IsOpened() const { return !Eof(); }
 
     // return true if we have anything to read, don't block
-    virtual bool CanRead() const;
+    virtual bool CanRead() const wxOVERRIDE;
 };
 
 class wxPipeOutputStream : public wxFileOutputStream
@@ -31,7 +31,7 @@ public:
 
     // Override the base class version to ignore "pipe full" errors: this is
     // not an error for this class.
-    size_t OnSysWrite(const void *buffer, size_t size);
+    size_t OnSysWrite(const void *buffer, size_t size) wxOVERRIDE;
 };
 
 #endif // _WX_UNIX_PRIVATE_PIPESTREAM_H_