A friendly user submitted the (lib)curl bug report #2154627 which identified a problem with our URL parser. It doesn't treat "file://" as a known protocol if the locale in use is Turkish.
So "file" and "FILE" are not the same word case insensitively in Turkish because 'i' is not the lowercase version of 'I'.
Back to strcasecmp: POSIX pretty much makes the function useless by saying that "The results are unspecified in other locales [than POSIX]".
I'm a bit annoyed by this fact, as now I have to introduce my own function (which thus cannot use tolower() or toupper() since they also are affected by the locale) and use since the strings in our code is clearly used for "english" strings so file and FILE truly are the same string when compared case insensitively...