Use OS-agnostic IO handlers

[hausdorf]

PROBLEM:

Current implementation of src/diff.c uses a method called load_file(). This opens a file given a directory. Arguably, though, this is a function that belongs in a file whose job it is to supply OS-agnostic IO handlers. As it turns out, this instinct is correct, as there is such a file, which you will see in the "resources" section.

OBJECTIVES:

• Transition diff.c to OS-agnostic IO handlers, to the exclusion of diff.c's load_file().
• Transition any other file that does this which I overlooked in this bug report.

RESOURCES:

• fileops.h and fileops.c supplies the OS-agnostic IO handlers required to complete this bug report. They're pretty easy to use.

[basepi]

Thanks for finding those fileops files, they were incredibly useful and, as far as I could see, feature-complete.

As far as I can tell, this issue is fixed. I have removed the load_files() method and the file_exists() method, refactoring all their uses with the equivalent methods from fileops.[h,c]. Closing it for now, if I've missed something, someone please re-open it, eh?

[hausdorf]

Glad to hear it.