Several users of the signal API used custom convenience classes to
invoke signal-handling functions on the reception of incoming signals.
The 'Signal_dispatcher' pattern turned out to be particularly useful. To
avoid the duplication of this code across the code base, this patch
adds the interface to 'base/signal.h'.
Furthermore, the patch changes the 'Signal::num()' return type from int
to unsigned because negative numbers are meaningless here.
Fixes#511
The recently added 'Genode::Path' class makes it easy to create absolute
paths. With this patch the 'ffat_fs' server uses the 'Genode::Path' class
where possible instead of working with 'f_chdir()' and relative paths.
This also solves the problem reported in issue #355, which was caused by
storing a relative file name in the 'File' node.
Fixes#355.
