Windows: Enable DPI-aware mode in Windows Assembly Manifest

This should solve display issues with HiDPI displays.
Closes #692.

geany.exe.manifest

@@ -15,4 +15,10 @@
 			</requestedPrivileges>
 		</security>
 	</trustInfo>
+
+	<asmv3:application xmlns:asmv3="urn:schemas-microsoft-com:asm.v3">
+		<asmv3:windowsSettings xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
+			<dpiAware>true</dpiAware>
+		</asmv3:windowsSettings>
+	</asmv3:application>
 </assembly>