Avoid ambiguous include guards in SG classes

These include guards stem from the olden days before the QSG
prefix and many of them are conflict prone, which can lead
to pretty bisarrer errors for the user.

Change-Id: I0e76c68a588404b6e82be9ecc2e7afa3b9a48e78
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>