Rename BLI_make_existing_file to BLI_file_ensure_parent_dir_exists.
The previous name read as if it would make (touch) the file,
where as it ensures the directory component of the path exists.
Move from BLI_path to BLI_fileops as path utilities should only
manipulate paths and not deal with file IO creation
(this has more in common with BLI_file_touch for e.g.).
1f96fa1129