uia: merge VCL pieces of IAccessible2 work.

Original code from:
    Author: Steve Yin <steve_y@apache.org>
    Date:   Sat Nov 16 23:58:19 2013 +0100

        Integrate branch of IAccessible2

With these improvements:

Make IAccessible2 an experimental feature, with fallback to Java a11y.
Move initial setup of windows into the bridge and clean, remove conditionals
Check for presence of AT in the bridge as well to clean. Merge VCL events
extensions and their handling. Clean and split WB_GETOBJECT handling out to
it's own method. Add component prefix namespacing.
Cleanup msaa service info, and implement XComponent to share mxAccessBridge.
Add suitable debugging output, remove VCL dependency from UAccCOM causing
registration issues.

Change-Id: Ib19e38ddca71182018df438df27dcdb555d91402