[MODULE] Clean module definitions.

 * Rename module initialization functions
   XXX_init() -> XXX_init_module(), XXX_fini() -> XXX_fini_module().
   This removes the confusion with non-module init functions.

 * Macro DEFINE_MODULE now provides the prototypes of the module
   so modules-specific headers do not need them. They should not
   be used on any other place anyway.
[GDIX,THEME] Use MC_TRACE_ERR instead of MC_TRACE where possible.