Commit d6029e974 with changes in dwg_add_Document() is bad.

Decoding process is:
* read numheader_vars from DWG file
* dwg_add_Document (which after this commit set this variable to different values)
* usage of numheader_vars

As I understand, we need to move this setting to dwg_new_Document()
Issue with reading of numheader_vars
This is a GitHub Issue
repo:libredwg
owner:LibreDWG
Title : Issue with reading of numheader_vars
Issue date:

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Commit d6029e974 with changes in dwg_add_Document() is bad.

Decoding process is:
* read numheader_vars from DWG file
* dwg_add_Document (which after this commit set this variable to different values)
* usage of numheader_vars

As I understand, we need to move this setting to dwg_new_Document()
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