It's probably rare for higher render targets to get locked or updated
from sysmem, but this should still be more correct. It also makes the
code simpler.

This ensures that we get the correct size for maximized windows too,
which cannot be done with SetWindowPlacement.

The parameter could have an offset of 0xffff/0xfffe, in which case the
parameter name should be the name of the function, rather than NULL.

This means that the string is NULL so don't attempt to access the
string data in this case.

Move it before loading of the constant data to allow better debugging
of problems during the processing of loading the constant data.

Also removes dirtifying of SCISSORTESTENABLE state that is made
redundant by ActivateContext(...,CTXUSAGE_CLEAR).