Remove the __NO_CTYPE define

Nothing within the project uses it, and it's not necessary to
build the project either, tested on both linux and mingw.
Remove an unused function

This function contains a lot of platform specific constants
whose use is unknown.
Merge pull request #175 from mstorsjo/remove-unused-define

Remove the __NO_CTYPE define
Merge pull request #177 from mstorsjo/remove-unused-function

Remove an unused function