Implement the following DxEng* functions:
- DxEngAltLockSurface
- DxEngDeleteSurface
- DxEngReferenceHdev
- DxEngSelectBitmap
- DxEngSetBitmapOwner
- DxEngUnreferenceHdev
Update their prototypes and call the appropriate win32k functions
inside them, since they are already implemented. Also get rid of
now unused IntGdi(Un)ReferencePdev, whose were called only by dxeng,
and whose are not used anymore. In Windows, DxEng(Un)ReferenceHdev calls
PDEVOBJ_vReferencePDEV and PDEVOBJ_vDeferencePDEV directly (those
correspond to our PDEVOBJ_vReference and PDEVOBJ_vRelease accordingly).
Required by MS DirectDraw stack (ddraw.dll & dxg.sys). CORE-17561
This will be used (later) to store the list of all enabled display devices.
Add a global variable gpmdev (should really be stored in DISPLAYINFO structure)
Replace global variable gppdevPrimary by pmdev->ppdevGlobal.