Cleaned up case related functions a bit
Made unsafely safe functions unsafe again, for safety
Added Ascii type
Added case functions to Ascii
Corrected history
Moved ascii out of str
Removed deriving Ord, which allowed to remove the stage markers
Added missing assert, did some formating
auto merge of #5980 : Kimundi/rust/ascii-encoding, r=thestinger

Added Ascii type to use for byte inputs that are known to contain Ascii only.