Compile without warnings

[henrygab]

This PR allows v0.14.0 to compile cleanly (no warnings), allowing end-users to focus on issues within their own code.

• Fixes [Bug] BlueFruit52 library -- uninitialized variable use #344 - Use of uninitialized variable in Bluefruit library
• Fixes [Bug] InternalFileSystem - compiler warnings from v0.14.0 flash cache read function #345 - InternalFileSystem compiler warnings for comparing signed vs. unsigned
• Fixes [Bug] Bluefruit52 library - Compiler warnings in v0.14.0 release #346 - Additional Bluefruit library compiler warnings

Note: I am not sure how to fully test these. I ran the bleuart example, and verified UART capability.

Of particular note is the changes to the InternalFileSystem library's flash_cache.c, function flash_cache_read(). Significant comments were added to help understand the implicit guarantees provided by the various code paths. A PowerShell function mirroring the original code flow was written to generate results from various parameters. A second PowerShell function mirroring the new code flow was written to validate those parameters ended up with the same actions occurring in the final code, including on all edge cases. Manual code review validated how the old code avoided some additional edge cases, and comments now explicitly document the implicit assumptions that the old code relied heavily upon for proper operation.

[henrygab]

Here's the simple PowerShell script I wrote to validate the logic changes:
https://gist.github.com/henrygab/d6d34d585ca3172f8ddf937658089af3

The first function references the line numbers as they exist now.
The second function corresponds to the logic in the PR.

Running the script will output the actions that would be taken for various inputs.
This includes where the parameters correspond to reads that:

• are entirely before the cache area
• end exactly at the start of the cache area
• begin prior to, and partially overlap, the cache area
• begin prior to, and extend past, the cache area
• begin at start of cache area, and read only cache area
• begin at start of cache area, and extend past the cache area
• begin at offset into cache area, and read only cache area
• begin at offset into cache area, and extends past the cache area
• begin exactly at the end of the cache area
• begin past the end of the cache area

Anyways, just wanted to show that work was done to validate the equivalence of the larger code change. Really, it's just a slight organizational change to allow the use of unsigned variables.

[henrygab]

rebase'd to latest master (8dbe7d9)

[henrygab]

Updating to remove additional compiler warnings at debug level 2.

[hathach]

Thank you very much, fixing lots of terrible warnings. And putting lots of effort into explaining how the read cache work. I actually intended to write a little more for it, but then hmmm, I guess I forgot :D. That is indeed very useful write-up :) . Great works!!!

[hathach]

Here's the simple PowerShell script I wrote to validate the logic changes:
https://gist.github.com/henrygab/d6d34d585ca3172f8ddf937658089af3

The first function references the line numbers as they exist now.
The second function corresponds to the logic in the PR.

Running the script will output the actions that would be taken for various inputs.
This includes where the parameters correspond to reads that:

• are entirely before the cache area
• end exactly at the start of the cache area
• begin prior to, and partially overlap, the cache area
• begin prior to, and extend past, the cache area
• begin at start of cache area, and read only cache area
• begin at start of cache area, and extend past the cache area
• begin at offset into cache area, and read only cache area
• begin at offset into cache area, and extends past the cache area
• begin exactly at the end of the cache area
• begin past the end of the cache area

Anyways, just wanted to show that work was done to validate the equivalence of the larger code change. Really, it's just a slight organizational change to allow the use of unsigned variables.

Thank you very much, this is very thoughtful of yours. Lots of effort to verify this, I should have done a better job of documenting :). Brilliant works and superb PR :)