PR modula2/111085 nexttoward and nexttowardf contain incorrect definitions

The definition for procedures nexttoward and nexttowardf contain
second incorrect parameter and return types.  This bug was
discovered when attempting to resolve PR 108143 and is applied
separately and prior to PR 108143.

gcc/m2/ChangeLog:

	PR modula2/111085
	* gm2-libs/Builtins.def (nexttoward): Alter the second
	parameter to LONGREAL.
	(nexttowardf): Alter the second	parameter to LONGREAL.
	* gm2-libs/Builtins.mod (nexttoward): Alter the second
	parameter to LONGREAL.
	(nexttowardf): Alter the second	parameter to LONGREAL.
	* gm2-libs/cbuiltin.def (nexttoward): Alter the second
	parameter to LONGREAL.
	(nexttowardf): Alter the second	parameter to LONGREAL.

Signed-off-by: Gaius Mulley <gaiusmod2@gmail.com>