Refactor and optimize type parsing a bit
Refactor and optimize type parsing a bit

Have BOOL/TRISTATE/... match _T_BOOL/_T_TRISTATE/... so that _set_type()
doesn't have to do any conversion in the common case. Conversion is
still needed for _T_DEF_BOOL/_T_DEF_TRISTATE/..., but those are rare.

Also make use of UNKNOWN being falsy.

Piggyback some rearranging of global constants so that related stuff
appears closer together, for readability.

ulfalizer/Kconfiglib,ulfalizer/Kconfiglib