XML generator and test

Fixes #1019
Add Attached_rom_dataspace::update

This patch enhances the 'Attached_rom_dataspace' utility to support
dynamic updates of ROM modules.
New 'os/attached_dataspace.h' utility

The new Attached_dataspace complements the existing Attached_*
utilities with a simple version that can be used with any kind of
dataspaces. It may be even useful as a common base type for the other
variants. For example, this patch simplifies Attached_rom_dataspace
and removes the Terminal::Client::Io_buffer.
util/string.h: String::operator ==
Dynamic ROM service for automated testing
Use filename as default label for ROM connections

By assigning the file name as label, we may become able to remove the
filename argument in the future by just interpreting the last part of
the label as filename. By keeping only the label, we won't need to
consider conditional routing (via <if-arg>) based on session arguments
other than the label anymore.
Minimalistic decorator for window system
Infrastructure for posting status reports

This commit introduces the "Report" session interface and a simple
service to forward reports to the LOG service.

Fixes #1026
nitpicker: Report pointer position
Service for reflecting reports as ROM modules

Issue #1026
Simple desktop environment (WiP)