Replace \u2011 (Non-Breaking Hyphen) with \x2D (Hyphen-Minus) in links

See merge request !1

The documentation uses non-ascii hyphens in some places. Some ended up
in links. Since the exact characters used in links matter this caused
links to be invalid.

Replace ndelay_off functions by io_set_block functions.

Using 'remove -P' cause issue due of the removed missing dependency for a service.
However, even if the graph displayed may not be strictly
exact for this case, a start command which required the missing dependencies
will be treat correctly as the system have trace of the
state of the dependencies graph for the entire system.
This is clearly ugly and a temporary fix. The graph function actually used will be dropped
in a near future due of the event features apparition.
Add STATE_FLAGS_MISSING flags

Review needed header files declaration and be clearer at variable name.

Add check target to handle test.

-wR can cause issue with notification readiness.

The fdholder will be freed to time. Let the shutdown algorithm handle it.