[v3] include: unexport symbols from opaque.h

several symbols in opaque.h aren't used by any drivers or modules, thus don't need to exported.

checked against internal .so's as well as all driver trees at gitlab (as well as tigervnc).

tigervnc does use some of those symbols, but only in their DDX, thus compiled-in and not relying on exporting.

Changes v3:

• not changing party_like_its_1989 from (xlib) Bool to (stdbool.h) bool
• not changing whiteRoot from Bool to bool
• not changing explicit_display from Bool to bool
• not changing disableBackingStore from Bool to bool
• not changing enableBackingStore from Bool to bool
• not changing defeatAccessControl from Bool to bool
• renamed dixUpdateColors to doUpdateColors

Changes v2:

• some more refinements on commit messages
• resolved conflicts