Forward-declare SfxModuleArr_Impl in sfx2/module.hxx.

This is only used within sfx2.

Change-Id: I40d850bcf82ba39dc7cf7d1a5b70c90add4e75c0
Move this header into source/inc.

Change-Id: I9127aaea3330b5c972ae7b3bf09912bc306d0f3c
Forward-declare SfxFrameArr_Impl in sfx2/frame.hxx.

Change-Id: I49f0a16655114bf212ffec957bc6560075115e5c