doc: added documentation to the global init defs

Documented the global init automaters:

	* subsys_init
	* module_init
	* device_init

Signed-off-by: Michel Megens <dev@michelmegens.net>
doc: init: documented the general system init.

Added documentation for the ETA/OS kernel initialisation. These
documents are found in the ETA/OS initialisation module.

Signed-off-by: Michel Megens <dev@michelmegens.net>
doc: delay: added docs to NOP delay functions.

Documented the looping delay functions:

	* delay
	* delay_us

Added CDECL and the CDECL_END CPP definitions to doxygen to stop them
from cluttering the documentation in unwanted ways.

Signed-off-by: Michel Megens <dev@michelmegens.net>
Merge branch 'dev-core'

* Docs on the automated init subsystem.
avr: init: removed some redundant init calls

Removed the old init CPP definitions which were used to beautify the
actual source code. Since the automated subsystem initialisation system
in in place, most of them aren't neccessary anymore.

Signed-off-by: Michel Megens <dev@michelmegens.net>
delay: config: added config opts for loop delays

Added the config options:

	* CONFIG_DELAY_US
	* CONFIG_DELAY_MS

Enabling delay_us and delay respectively. Especially `delay' should be
handled with care for scheduled applications, since it has the nasty
side effect of derailing the scheduler and virtual timers. When using
the scheduler `sleep' should be used instead.

Signed-off-by: Michel Megens <dev@michelmegens.net>
ETA/OS 2.0.0

Signed-off-by: Michel Megens <dev@michelmegens.net>