[rpi] Enable "turbo mode".

Use the "turbo mode", i.e. the overclocking settings approved by the makers
of the Raspberry Pi [1]. The clock values are taken from the "Raspbian"
image, the official Raspberry Pi distribution [2].

[1] http://www.raspberrypi.org/archives/2008
[2] http://www.raspberrypi.org/archives/2008#comment-33059

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>
[rpi] Wait for the ethernet chip to be ready.

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>
[rpi] Add an 'install' target to write the SD card.

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>
[PKG] Add a package for the LZO library.

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>
[PKG] Add a package for OpenVPN.

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>
[PKG] networking: Copy /etc/resolv.conf if file is available.

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>
[PKG] linux: don't overwrite the header files in the staging directory.

The 'headers_install' target of the kernel build system apparently clears
the destination directory before it installs the kernel headers. Therefore,
install them into a temporary directory and copy them over.

Signed-off-by: Jens Steinhauser <jens.steinhauser@gmail.com>