line 356: remark(1174): parameter "dev" was declared but never referenced

This is true when ISC_NET_BSD44MSGHDR is not defined.  UNUSED()s were added.

line 1580: remark(1552): variable "task" was set but never used
line 1670: remark(1552): variable "task" was set but never used

I removed the stack variable and its assignment in each case.

line 2915: remark(1552): variable "ret" was set but never used

It was apparent that the variable was meant to be the return value
of isc_socket_getsockname, so the return statement was changed to use it.

Also ...

Changed function declarations to ISC coding style.

Wrapped two lines that were wider than column 79.

Removed two UNUSED() macros for variables that were no longer unused.