--sectionnameonly does not work for LaTeX

When using LaTeX output (i.e. --latex), the option --sectionnameonly has no effect.
It can very easily be implemented though, by replacing in Source/latex_generator.c:

```
cur_header->name
```

with

```
course_of_action.do_sectionnameonly ? cur_header->function_name : cur_header->name
```

The combination --latex --sections also has no effect, but that bothers me less.
