Blender Git Loki

Cleanup: alias: use const, remove unused variable.

`targetIsDirectory` slipped through the code review of
{D6679}/{rBafb1a64ccb81}.
`BLI_is_dir` exists to check for directory status of a file.

Remove some `else-after-return`s.

Use `r_` prefix for return value arguments, and move it to the end
in the list of arguments.