WIP: cleanup CCOS-disk-utils

[vklachkov]

One more step to make this library safe to use in a future FUSE driver.

Too much stuff happened during the refactoring process. If necessary, I'll split this PR into three separate ones.

Done:

• use errno codes instead of -1
• fix compilation on old compiler, use C99 standard
• fix all known memory leaks
• fix UB in ccos_create_dir
• fix clang format

In progress:

• thinking about replacing the errno codes with own error codes (this will allow remove all error printf's)
• one more valgrind run, one more sanitizers check and maybe check project with sonarqube
• doxygen

[BOOtak]

It would be better to split this PR into separate ones:

• first with clang-format fixes and re-formatting all the code with fixed clang-format. If the code is already formatted correctly, you can submit clang-format changes with another PR
• second PR: API changes. Those should include return codes (-errno vs -1, function name and signature changes, etc.)
• third PR: code hardening. Those changes should include CMake option to make sanitized build (ASan, UBSan), strict compilation flags (-Werror -Wall -Wextra -penantic?) - you can apply as many or as little extra warnings as you wish, because right now there are none, so any change in this direction is welcome :)

[vklachkov]

Yes, I agree, there are too many changes, they need to be split.