cppcheck-detected code issues

A number of issues were detected in commit efff347f on May 21. Those which don't appear to be down to things like cppcheck not noticing that a REQUIRE has already checked for a pointer being non-null are:

lib/irs/win32/resconf.c(35)
Variable 'keyFound' is assigned a value that is never used.

lib/isc/tests/mem_test.c(410)
Variable 'f' is assigned a value that is never used.

lib/isc/tests/mem_test.c(531)
Variable 'size' is assigned a value that is never used.

lib/isc/unix/net.c(399)
Unused variable: flags.

lib/isc/win32/app.c(83)
Unused variable: result.

lib/isc/win32/app.c(169)
Variable 'pHandles' is assigned a value that is never used.

lib/isc/win32/socket.c(2478)
Unused variable: result.

lib/samples/nsprobe.c(110-115)
A number of fields in the lcl_stat structure have the same name as the query_result_t enum constants and cppcheck complains that "Variable 'XXX' hides enumerator with same name".

The full cppcheck output can be found on Jenkins here.