Filesystem refactor and update

[a740g]

Closes #34
Closes #148

This pull request represents a significant refactoring effort to consolidate all filesystem-related APIs into their own translation unit inside libqb/. It now correctly handles all APIs, including some that were previously only implemented for Windows, across all supported platforms. This also auto-corrects directory separators in func__loadimage(), sub__saveimage(), func__sndopen() and func__loadfont().

The following two new functions were added:

' MS BASIC PDS 7.1 & VBDOS 1.0 DIR$() style function 
_FILES$([fileSpec$])

' Returns the Fully Qualified Name for a file / directory
_FULLPATH$(pathName$)

[SteveMcNeill]

I'm not so certain about the _FQN name. Honestly, I don't think it's a set of abbreviations that's going to mean a whole lot to the old foggies who tend to program in BASIC a lot. As much as I hate extra typing, I'd think a more verbose name might be needed here to maintain the general style as BASIC programming. Perhaps something like _FULLPATH. Or could these two functions somehow be combined into one?

_FILES$ (filespec$ , "verbose|brief")

Being picky over a command name seems almost petty in many ways, but this is very useful functionality. You want to try and make it as intuitive for the general user as possible, when you add it into the language.

[SteveMcNeill]

(Even if it is kept as a short command name, shouldn't it at least be _FQFN for a Fully Qualified File Name? )

[a740g]

I'm not so certain about the _FQN name. Honestly, I don't think it's a set of abbreviations that's going to mean a whole lot to the old foggies who tend to program in BASIC a lot. As much as I hate extra typing, I'd think a more verbose name might be needed here to maintain the general style as BASIC programming. Perhaps something like _FULLPATH. Or could these two functions somehow be combined into one?

_FILES$ (filespec$ , "verbose|brief")

Being picky over a command name seems almost petty in many ways, but this is very useful functionality. You want to try and make it as intuitive for the general user as possible, when you add it into the language.

BASIC itself is not consistent with names. 😁 FRE, MK* and CV* are some that comes to mind. But I too am with you on verbose names. I initially thought of _FULLYQUALIFIEDNAME but quickly dropped it after looking at the number of characters. 😊 _FULLPATH sounds good though. We should not combine _FULLPATH and _FILES because we should allow folks to get canonicalized absolute pathnames without going thought the internal setup that _FILES does.

I'll change _FQN to _FULLPATH unless someone has any other suggestions.

[a740g]

(Even if it is kept as a short command name, shouldn't it at least be _FQFN for a Fully Qualified File Name? )

Well, it works for both file names and directory names. So, I not sure if we should use _FQFN. 🤷‍♂️

[SteveMcNeill]

_FULLPATH sounds good to me, unless anyone else has a better suggestion. Otherwise, from what I can tell looking over this, it all looks good to me. :)