KWSys: Remove dependencies on FundamentalType

The hash_fun.hxx header is configured whether FundamentalType is enabled
or not and so cannot depend on it.  Run the relevant platform tests
whether or not FundamentalType is on and configure the result directly
into hash_fun.  While at it, remove the dependence of SystemInformation
on FundamentalType too since it needs only information that we now
always compute.