Change chtype = cint to chtype = uint32

[HJarausch]

The line
u1: cint = 1
A_NORMAL* = (u1 - u1)
A_ATTRIBUTES* = NCURSES_BITS(not (u1 - u1), 0)

crashes nim since not (u1 - u1) is a 64 bit value (on my amd64 machine) which cannot be converted to chtype

Replacing the first line by
u1:uint32= 1
fixes the issue
This is with
Nim Compiler Version 1.5.1 [Linux: amd64]
Compiled at 2020-11-20
Copyright (c) 2006-2020 by Andreas Rumpf

git hash: fcb2ec4ed69fe924e7e3899e0084f534124255d4
active boot switches: -d:release