small cleanups to module.h and loader.c to start playing with

new-style modules using static symbols.

Everything will still work as before, but new-style modules
can now be defined by putting a '#define STATIC_MODULE' somewhere
before including module.h, then declaring STATIC_MODULE the
various methods (load, unload, key...) that the module is
supposed to supply, and adding a 'STD_MOD(MOD_1, reload_fn, NULL, NULL)'
macro call at the end.
A module compiled in this way will be loaded RTLD_NOW|RTLD_LOCAL
so symbol pollution is reduced, and symbols are resolved immediately.
Removing just the '#define STATIC_MODULE' will restore the old
behaviour.

In order for a module to be loaded RTLD_NOW|RTLD_LOCAL, it must not
export any symbol[1], and all the modules it depends on (e.g. res_*)
must be loaded already.

[1] Mechanisms are in place, and will be enabled later, to still
allow such modules to 'export' symbols and resolving the dependencies
irrespective of the load order.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@17790 65c4cc65-6c06-0410-ace0-fbb531ad65f3