vcl: remove SalVirtualDevice::GetWidth

It is presumed that #i59315# is fixed already, and that this is no
longer necessary.

Change-Id: Ifb2f6550fac2481c4fec269b38d6e806753cb53e
vcl: create a GeometryProvider interface.

Implemented by both SalFrame and SalVirtualDevice, to help us to
un-tangle code that needs to operate on resources associated with
both of these without special cases.

Change-Id: If681a002647e20c57186577fe039d4ac85bba872
vcl: Consolidate size information around the GeometryProvider.

Change-Id: I1d764a8dba1850d2475f08e1014a085846f336c3
vcl: re-init windows graphics impl after virtualdevice size change.

Change-Id: I6188617aa2cf2e237ec0724d1442564fbf3fe297
Werror, Wunused-variable

Change-Id: Ia361b1e37ad8b0daf49ff236c855a70d7d8bf8f4
implement virtual methods for OSX vcl backend

Change-Id: Ifd7e06529cbf2e20bdd1560586420cda39c5a50c