Correct DPI context awareness value retrieval

[HeikoKlare]

Tracking ticket for:

• [Win32] Correct DPI context awareness value retrieval eclipse-platform/eclipse.platform.swt#2985

Branch with generated DLLs is available here:
https://github.com/vi-eclipse/eclipse.platform.swt/tree/proper-dpiawareness-retrieval-withdlls

This is a prerequiste for:

• Enable monitor-specific scaling by default in SWT #582