classicladder: give the headers include guards and their own dependencies

[grandixximo]

30 of the 34 headers in hal/classicladder have no include guard, and 12 do not compile on their own. They name StrRung, StrStep, cairo_t or the gtk types without including whatever declares them, and build only because the file that included them had already got there.

Guards go in first, since including classicladder.h from twelve places without them redefines everything. Then the twelve name what they use.

The guards are CLASSICLADDER_<FILE>_H. The four that had one already used a leading underscore, which is reserved to the implementation, so they are renamed rather than left as a second convention in one directory.

Testing. All 34 compile standalone afterwards, one translation unit per header, where 22 did before. Built clean with --with-realtime=uspace, no errors and no warnings.

Is it worth having? @BsAtHome this is your point from #4425, that a header needing something should be the one to say so, applied to a subsystem you did not ask about. classicladder is old code nobody is working on, so if 34 files of churn reads as noise, say so and I will close it.

Independent of #4425, overlapping by one line, the <stdio.h> in files.h.

[rmu75]

Adding to the noise: is there a reason not to use #pragma once? While not in any C/C++ standard it is probably even rarer for a compiler to not support that than non-two's complement int representation.