Refactor debugging/visualisation functions

[hypirion]

The functionality currently residing within rrb_debug.h has slowly evolved over time through what I needed for debugging, and is not really conforming to C calling conventions nor handling errors in a preferable way. These functions should be refactored to idiomatic C functions while retain the very "easy-to-use" functionality they have within lldb/gdb.

Should solve the issues mentioned in #1.

[elfring]

I would appreciate that the debugging functionality will also become configurable by build options.

[hypirion]

@elfring That is already possible through --enable-rrb-debug and --disable-rrb-debug, or is that not what you are talking about?

[elfring]

I'm sorry. - It seems that I overlooked this build option.

Another implementation detail might also matter.

• Which debug functions will be moved to a ".c" file from the current header?
• Are you interested in fine-tuning for function inlining?