Add support for a message queue for each application

[noxer]

To enable inter-process-communication and notifications there should be a message queue for the applications.

-> each process has a buffer that any other proccess can write to, which is read by the buffer owning process

[rustyoz]

can you expand on this? i might have a crack at it.
do you mean:

• each process has a buffer that any other proccess can write to, which is read by the buffer owning process
• or a single buffer that every proccess can read and write from?

[noxer]

The first. Except the kernel writes to the buffers. A process can call msg_send_to to send a message to a specific process but has no direct access to the buffers of other processes.

[rustyoz]

there is already chessmaster's message routines, is that what you had in mind noxer? is seems like it is more the second model with the common buffer.

[noxer]

These routines are the first part of my implementation (chessmaster moved them into the file so its shown as his commit) but they are missing a possibility for sending a message to a specific process.
With msg_queue_reg you register a part of the memory as a message queue so the OS can deliver the messages. A global message queue would make it impossible to determine if a message has been read by all running processes. But I think we need to make the queue longer (eg. 32 or 64 words).