vcl: fix some "cannot convert 'objc_object*' to..." issues

Change-Id: I4b0e32c412937da4b2ea4bf350be32ea31362b3c
workarounds for `objc_msgSend' on 10.5

(vcl/osx/salframe.cxx, vcl/osx/salmenu.cxx)

plus, move conditional includes in salframe.cxx down a bit

Change-Id: I39886b4590f227ec69042fed0f5240ba0b0fd7f2