[vali] memory-mapped files

[Meulengracht]

Is your feature request related to a problem? Please describe.
We encounter more and more projects that rely on memory mapped files, and to be honest its a great feature to support. So we should implement a way to support this.

Describe the solution you'd like
We would like to implement the dummy interface described in os/mollenos.h that actually has two methods for creating/destroing memory mapped files.

Additional context
The implementation should consists of two parts:

• Modify any existing protocol if neccessary, I'm assuming we need a few new calls.
• Implement support for memory handlers in the kernel, so the kernel can proxy events to a service when a process tries to access a predefined memory area (the memory map of the file).
• Implement the actual handling of the memory mapped files in the filemanager service.