[DAEMONS] Add a monitor daemon, with compatibility with framebuffers.

This patch adds a monitor daemon which periodically writes CPU, RAM and VCPU
information on a character device.
A new IOCTL has been defined for periodically erase the character device.
IOCTL definition macros have been added.
[DRIVERS] i.MX IPU, framebuffer and pixel clock debugging removed.
[DRIVERS] SDHCI Present State checking corrected.
[DRIVERS] SDHCI DMA operation enabled back (temporary hack).
[DRIVERS] The i.MX uSDHC controller use physical address for its DMA.
[DRIVERS] Correcting the i.MX uSDHC driver on bus width management.

The original i.MX uSDHC driver expected the "esdhc_pltfm_bus_width" function to
be called, managing the bus width in the host controller register.
Since this function is called by the "platform_bus_width" operation, removed in
Xvisor, this must be done the usual way, hence when writing this register.
[DRIVERS] Temporary MMC hack to do only single block read operations.

As the i.MX uSDHCI driver does not work with multi block operations yet, the
single operation is forced for now.
[DRIVERS] SDHCI pio operations must not be done when using DMA.

It seems that even with DMA activated, the SDHCI driver still does a controller
buffer reading, sometimes leading to a read data buffer overwritting.
[COMMANDS] Add a blockdev read command.

This patch adds a read command for block devices, allowing to read data from
it.
Arguments:
- the device name (mandatory)
- the amount of data in bytes to read. If not specified, it will take the
  device default block size.
- the offset in bytes.
[LIBS] Add a simple image loader for framebuffer splash screen.

This patch adds a simple image loader, managing only the P6 ppm format with
less that 256 colors, allowing framebuffer splash screen.
[COMMANDS] Adding the "fb image" command, to display an image on a framebuffer.

This "fb image" command takes the following argument:
- the framebuffer to display the image on
- the image path
- the "x", the horizontal offset on the screen
- the "y", the vertical offset on the screen