Converts an OCaml number to a canonical integer literal of type :real.
DESCRIPTION
The call mk_realintconst n where n is an OCaml number (type num) produces
the canonical literal of type :real representing the integer n. This will
be of the form `&m' for a numeral m (when n is nonnegative) or `-- &m'
for a nonzero numeral m (when n is negative).
FAILURE CONDITIONS
Fails if applied to a number that is not an integer (type num also includes
rational numbers).
EXAMPLE
# mk_realintconst (Int (-101));;
val it : term = `-- &101`
# type_of it;;
val it : hol_type = `:real`