Changes to recent addition: c85c52f2ce.
Having both BLI_paths_equal and BLI_path_cmp made it ambiguous
which should be used, as `BLI_paths_equal` wasn't the equivalent to
`BLI_path_cmp(..) == 0` as it is for string equals macro `STREQ(..)`.
It's also a more specialized function which is not used for path
comparison throughout Blender's internal path handling logic.
Instead rename this `BLI_path_cmp_normalized` and return the result of
`BLI_path_cmp` to make it clear paths are modified before comparison.
Also add comments about the conventions for Blender's path comparison
as well as a possible equivalent to Python's `os.path.samefile`
for checking if two paths point to the same location on the file-system.