[darwin] SysInfo::GetKernelBitness: Use special function for Darwin iOS
[darwin] SysInfo::GetKernelCpuFamily: Use special function for Darwin
TestSystemInfo: print system information
SysInfo::GetKernelBitness: cache result
SysInfo::GetKernelCpuFamily: cache result

Conflicts:
	xbmc/utils/SystemInfo.h
Merge pull request #5001 from Karlson2k/darwin_host_id_01

Fix Darwin host identification