-Werror=class-memaccess (trunk towards GCC 9)

..."‘void* memset(void*, int, size_t)’ clearing an object of type ‘struct
HWPDrawingObject’ with no trivial copy-assignment; use value-initialization
instead" after 96c85e7d "loplugin:useuniqueptr
in hwpfilter"

Change-Id: Iee2b0ba2ec57233a311c88cb904af2bae71286d0
Reviewed-on: https://gerrit.libreoffice.org/65375
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

hwpfilter/source/drawing.h

@@ -677,9 +677,11 @@ int cmd, void * /*argp*/, int /*argv*/)
 }
 
 
-HWPDrawingObject::HWPDrawingObject()
+HWPDrawingObject::HWPDrawingObject():
+    type(0), offset{0, 0}, offset2{0, 0}, extent{0, 0}, vrect{0, 0, 0, 0}
 {
-    memset(this, 0, sizeof(HWPDrawingObject));
+    memset(&property, 0, sizeof property);
+    memset(&u, 0, sizeof u);
     index = ++count;
 }