Revert component-split

this reverts the commits from 92ab9ef52e up to
d42870d6ca.

After heavy consideration, the component split has more disadvantages
than advantages, especially given there will be utility-functions
sharing quite a lot of code that would then need to be duplicated, as it
does not fit into the util.c due to its speciality.

One big advantage of the component-wise build is readability, and
without doubt, this was achieved here. This point will be addressed
with a different approach that will be visible in the upcoming commits.

One big disadvantage of the component build is the fact that it
introduces state to the build process which is not necessary. Before its
introduction, the only influencing factors where the system-defines
__linux__ and __OpenBSD__. With the components, we are also relying on
the output of uname(1).
Additionally, if the os.mk is not present, make gives the output

     $ make
     Makefile:5: os.mk: No such file or directory
     make: *** No rule to make target 'os.mk'.  Stop.

This could easily be fixed by providing some sort of meta-rule for this
file, however, it indicates the problem we have here, and this entire
statefulness will heavily complicate packaging of this tool and makes
the build process much more complex than it actually has to be.

LICENSE

@@ -7,7 +7,7 @@ Copyright 2016 Vincent Loupmon <vincentloupmon@gmail.com>
 Copyright 2016 Daniel Walter <d.walter@0x90.at>
 Copyright 2016-2018 Ali H. Fardan <raiz@firemail.cc>
 Copyright 2016 Jody Leonard <me@jodyleonard.com>
-Copyright 2016-2018 Quentin Rameau <quinq@fifth.space>
+Copyright 2016-2017 Quentin Rameau <quinq@fifth.space>
 Copyright 2016 Mike Coddington <mike@coddington.us>
 Copyright 2016-2018 parazyd <parazyd@dyne.org>
 Copyright 2017 Tobias Stoeckmann <tobias@stoeckmann.org>