Fix a few problems in the iOS vcl code

We don't need the headless SvpSalBitmap code after all on iOS, so
bypass all of svpbmp.cxx for iOS.

I accidentally had left duplicates for some AquaSalGraphics methods in
headless/svpgdi.cxx in addition to the ones in
quartz/salgdicommon.cxx. This is obviously bogus, the linker just
picks the ones that come first in the archive.

(Remember the ugly "#define SvpSalGraphics AquaSalGraphics" trick, so
for instance SvpSalGraphics::setClipRegion actuall is
AquaSalGraphics::setClipRegion.)

It's the Quartz ones we want, as since the switch to tiled rendering
the iOS vcl code is supposed to work much more like the OS X
one. (There is still some significant refactoring to do
there. Possibly no "headless" code needs to be used at all for iOS.)

A couple of functions moved from salgdiutils.cxx (which isn't compiled
for iOS) to salgdicommon.cxx.

The SetState() function now gets used also on iOS, and to properly
undo its CG context stacking I pop it in SetVirDevGraphics() when the
virtual device is being destroyed.

This fixed the rendering of some simple shapes that use overlapping
and transparency, but not that of the "monster" SmartArts.

Change-Id: I2bfaa4129e3641dbdd1dd240c1d07f9bdcfea1b8