It handles exit() properly, calling the handler also when the plugin returns
normally (also it makes exit() more standard compliant while at it).
It also holds PLUGIN_HEADER, so that it doesn't need to be in each plugin anymore.
To work better together with callbacks passed to rb->default_event_handler_ex introduce exit_on_usb() which will call the exit handler before showing the usb screen and exit() after it.
In most cases it was passed a callback which was manually called at all other return points. This can now be done via atexit().
In future plugin_crt0.c could also handle clearing bss, initializing iram and more.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27862 a1c6a512-1295-4272-9138-f99709370657
struct plugin_api *rb is declared in PLUGIN_HEADER, and pointed to by
__header.api
the loader uses this pointer to initialize rb before calling entry_point
entry_point is no longer passed a pointer to the plugin API
all plugins, and pluginlib functions, are modified to refer to the
global rb
pluginlib functions which only served to copy the API pointer are
removed
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19776 a1c6a512-1295-4272-9138-f99709370657
