collada2gltf: drop tr1 support

The detection code is wrong for gcc 4.6 and the tr1 code actually
conflicts with the OpenCOLLADA code, because it creates an ambiguity
of shared_ptr in the cpp files.

Additionally most of the headers already use std::shared_ptr or
std::unordered_map.

Change-Id: Ibfe80e45687d34ec6fcd23339fd3f968fae402ba
Reviewed-on: https://gerrit.libreoffice.org/11695
Reviewed-by: Zolnai Tamás <tamas.zolnai@collabora.com>
Tested-by: Zolnai Tamás <tamas.zolnai@collabora.com>