QAxBase doesn't expose class context properties

The QAxBase::setControl method doesn't provide any mechanism for configuring the "class context" for the ActiveX control. Instead, it's hardcoded to always pass CLSCTX_SERVER when calling CoCreateInstance to create the control.

Introduction of configurable "class context" would enable programmatic switching between in-proc and out-of-proc startup of ActiveX controls that support both alternatives. It could also enable startup of the control in a restricted "sandboxed" environment if used together with CLSCTX_ENABLE_CLOAKING and an impersonation token.