c_glib: Generated code tries to convert between function and void pointers

In code generated by the compiler for C (GLib), a service's processor class incorrectly treats function and void pointers as interchangeable: When adding to the process_map hash table it supplies a pointer to a function, while g_hash_table_insert expects a gpointer (effectively void *) to a data object.

ISO C explicitly forbids this conversion as it is not compatible with all architectures, and with its -pedantic option enabled gcc will generate warnings like

gen-c_glib/calculator.c: In function 'calculator_processor_init':
gen-c_glib/calculator.c:1231:24: warning: ISO C forbids passing argument 3 of 'g_hash_table_insert' between function pointer and 'void *' [-Wpedantic]
                        calculator_processor_process_ping);

The compiler needs to be fixed so the code it generates does not try to use function pointers where data (void) pointers are expected.