Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 atom_t(Arg1)

 integer_t(Arg1)

 float_t(Arg1)

 rational_t(Arg1)

 number_t(Arg1)

 string_t(Arg1)

 atomic_t(Arg1)

 compound_t(Arg1)

 callable_t(Arg1)