Related: #i123795# add a windowForParent() method for AquaA11yWrapper

for getting the parent window of an A11y enabled NSView. The method
viewElementForParent() was abused for that purpose, but it was mis-named
and mis-typed. The new method cleans this up and the now unused
viewElementForParent() method can be retired.

(cherry picked from commit 96cd47d49a3aa5b1e3b96b649f40e516ca568d4b)

Conflicts:
	vcl/osx/a11ywrapper.mm
	vcl/osx/salframeview.mm

Change-Id: Ib88aa1ad442d3b8fb3adbf7a76b3ed8ca268fa87

(cherry picked from commit a7d6569fdecc36bd5ca093442a9b7aec093637d5)