Gerbview: Deprecated Commands in older Gerber Files lead to 'Unexpected char' Errors

Description

Older 3rd party Gerber files containing deprecated commands like %IPPOS*% cannot be opened since v9. That's not very practical.

Steps to reproduce

1. Try open in Gerber Viewer:

   test.gbr

KiCad Version

Application: KiCad Gerber Viewer x64 on x64

Version: 9.0.4, release build

Libraries:
	wxWidgets 3.2.8
	FreeType 2.13.3
	HarfBuzz 10.2.0
	FontConfig 2.15.0

Platform: Windows 11 (build 26100), 64-bit edition, 64 bit, Little endian, wxMSW
OpenGL: Intel, Intel(R) UHD Graphics 630, 4.6.0 - Build 31.0.101.2134

	wxWidgets: 3.2.8 (wchar_t,wx containers)
	Boost: 1.88.0
	OCC: 7.9.1
	Curl: 8.13.0-DEV
	ngspice: 44
	Compiler: Visual C++ 1942 without C++ ABI
	KICAD_IPC_API=ON

Locale: 
	Lang: en_GB
	Enc: UTF-8
	Num: 1,234.5
	Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)