Specifically, the `BE_CIRC` is an alt-ed keycode, which means it 
doesn't fit into the 8 bit keycode range...  It should be `BE_SECT`,
as it is already alt-ed by the alt lut.

Confirmed that this change fixes compilation warnings and works 
correctly, on reddit. 
https://www.reddit.com/r/olkb/comments/iywin1/unsigned_conversion_from_int_to_unsigned_char/g6jvfgl/