Avoid warning from C compiler about mismatched pointer types.

Avoid warning from C compiler about mismatched pointer types
when the --optimise-constructor-last-call optimisation is enabled
in high-level C grades.

compiler/ml_unify_gen.m:
	Cast the pointer of a cell field to the type of the address
	variable that will hold it.
Fix the documentation of map.union/4.

library/map.m:
	Add a missing word.

	Refer to the higher-order argument as a closure rather than
	a predicate since the description covers both the function
	and predicate versions of map.union.
Merge branch 'version-13_05-branch'
Add some more standard library procedures.

library/bimap.m:
	Add a predicate for testing semantic equality of bimaps.

library/assoc_list.m:
	Add fold_values with two or three accumulator arguments.

library/int.m:
	Add fold_{up,down} with three accumulator arguments.

library/map.m:
library/tree234.m;
	Add foldl_values with two or three accumulator arguments.

NEWS:
	Announce the above additions.

	Reformat the existing changes to the pqueue module slightly
Add det_take to the list module

The list module currently contains take, drop and det_drop predicates, but
no det_take predicate.  Developers could use det_split_list instead, however
det_take is more straight-forward and can be expected to exist since
det_drop exists.

library/list.m:
    As above.

NEWS:
    Announce the new predicate.