This fixes cppcheck warnings (style) 'class x' does not have a copy constructor
which is recommended since the class contains a pointer to allocated memory.
issue, but brings less noise about memory leaks when using valgrind).
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@39864 a592a061-630c-0410-9148-cb99ea01b6c8