This patch fixes some (mostly small) plugin issues with the "big"
YH-keymap patch (a507b). Only one fix affects the main keymaps
(virtual keyboard "DONE" now exits after long key /release/ instead
of long button /press/).

Change-Id: Id34f925ebfa97ae4974cd9405fbe1fee4f597833

The main "innovation" in this patch are two "virtual buttons"
for the record switch on YH92x targets. When the switch state
changes, a single BUTTON_REC_SW_ON or .._OFF button event will
be generated. Thus keymap code can react on switching, but
not on the actual state of the switch.

Wherever sensible, the following user scheme is applied:
- use PLAY as confirm button
- use REW button or Long REW to exit
- use REC (YH820) or FFWD (YH92X) as modifier key for button combos

Change-Id: Ic8d1db9cc6869daed8dda98990dfdf7f6fd5d5a1

Additional status callback is added to pcm_play/rec_data instead of
using a special function to set it. Status includes DMA error
reporting to the status callback. Playback and recording callback
become more alike except playback uses "const void **addr" (because
the data should not be altered) and recording  uses "void **addr".
"const" is put in place throughout where appropriate.

Most changes are fairly trivial. One that should be checked in
particular because it isn't so much is telechips, if anyone cares to
bother. PP5002 is not so trivial either but that tested as working.

Change-Id: I4928d69b3b3be7fb93e259f81635232df9bd1df2
Reviewed-on: http://gerrit.rockbox.org/166
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested-by: Michael Sevakis <jethead71@rockbox.org>

Move to plugin_crt0.c, plugins don't need PLUGIN_IRAM_* macros anymore
IRAM is no longered zeroed before copying (as it is at the same address
than BSS) -> Fix FS#11581
Use cpucache_invalidate() (and not cpucache_flush), needed for self-modifying code on cached IRAM

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27948 a1c6a512-1295-4272-9138-f99709370657

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27926 a1c6a512-1295-4272-9138-f99709370657

It handles exit() properly, calling the handler also when the plugin returns
normally (also make 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 rb->default_event_handler_ex() 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@27873 a1c6a512-1295-4272-9138-f99709370657

Too much errors and no time to fix them now.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27863 a1c6a512-1295-4272-9138-f99709370657

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

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27208 a1c6a512-1295-4272-9138-f99709370657

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27203 a1c6a512-1295-4272-9138-f99709370657