[refactoring] General maintenance

[Nightwalker-87]

The following tasks should be achieved to improve the codebase of the toolset:

• modularise the codebase
• reduce cross-dependencies between headers and source files where possible
• separate device-specific settings from source code ([refactoring] Moved chip-specific parameters into separate files #1129)
• rewrite and modularisation of: chipid.c chipid.h common.c stlink.h stm32.h
• allow general use of core-IDs for MCU identification ([code-structure] Add all STM32 Core-IDs to the codebase for MCU identification #903)

Some intentions on general proceedings (priorised):

1. Simplification / Clean-up / Restructuring
2. Correction of data types based on C/C++ Reference and common recommendations
3. Evaluation on how to commonly include Cortex-M core ids (CPUTAPID) in the workflow of device identification
4. Definition of structures to prepare for future ABI compatibilty
5. Update for the stlink-lib documentation

[Nightwalker-87]

@Ant-ON @slyshykO I have just pushed a new commit to branch chipid_cleanup with some further preparations.
Can you have a look at it, give some feedback and verify functionality. I did some basic tests with a STM32 VL Discovery board but not too many yet. Also additional hardware to test with is currently out of reach...

[Nightwalker-87]

Based on the original intention to solely complete the separation of chip-specific parametres out of the source code and into device-specific files led to some more general clean-up and restructuring. Nevertheless work is not complete of course...
I believe that the source code and header files stm32.h, chipid.c and chipid.h are on a good way to reach structure and content as we may expect them to be and to serve as.

For now I am going to make a halt here to give everybody a chance to follow the changes which appear quite huge already.
Please let me know if you deserve a PR to be opened before continuing with other topics.

[Nightwalker-87]

... and BTW: When does

#ifdef __cplusplus
    extern "C" {
#endif

[...]

#ifdef __cplusplus
}
#endif

exactly make sense?

[slyshykO]

... and BTW: When does

#ifdef __cplusplus
    extern "C" {
#endif

[...]

#ifdef __cplusplus
}
#endif

exactly make sense?

It needs for whom who uses our includes in C++ code.

[Nightwalker-87]

Tell me a story, I got that far, but the question is: Where is it necessary from the technical perspective. It is not in general, because otherwise it would be defined in every source code file, which isn't the case and compilation and execution in C++ is known to be working anyway.