temporary quickfix for issue #3473

Missing fclose in tinyobj loader.

WARNING: OBJ loading is broken at this point...

* allow for multiple materials in obj files also fix obj_loader hash map issues

* minor fix for warning

Co-authored-by: codifies <nospam@antispam.com>

This reverts commit 53b32f1c20.

This is quite a big change, Model struct has been redesigned to support multiple meshes and multiple materials, most 3d fileformats contain multiple meshes and reference multiple materials.

Consequently, multiple functions have been reviewed.

LoadOBJ(), LoadIQM(), LoadGLFT() now return a Model.

Current LoadOBJ() is not valid anymore, actually, tinyobj_loader_c library is considered for replacement.