Add TotalPhysicalMemory to dxGetStatus

[Pirulax]

Allow scripters to get access info about available total physical memory. There's a very slight difference between the actual physicals memory and this (since there's some memory reserved for the hardware (exact value can be seen in task manager))

[Dutchman101]

If PR #2267 gets accepted, it should probably supersede this (there'd be no need for also getting RAM in dxGetStatus).

But if for some reason that PR can't pass, this PR (adding it to dxGetStatus) will be the minimum feature required to implement PR #1677 (Allow load custom IMG containers).

[Pirulax]

Im going to leave this one here, just in case. But the other one should be more than enough.