pcbnew always plot Gerber files with X2 netlist extension

[Eldar Khayrullin]

I want to have possibility to disable Gerber X2 netlist extension for commercial restrictions.
Now if Gerber X2 disabled then netlist embedded to gerber files as comments always.

Application: kicad
Version: 5.0.2-bee76a0~70~ubuntu18.10.1, release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.61.0 OpenSSL/1.1.1 zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.4) nghttp2/1.32.1 librtmp/2.3
Platform: Linux 4.18.0-12-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.67.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.61.0
    Compiler: GCC 8.2.0 with C++ ABI 1013

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_WXPYTHON=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[jean-pierre charras (jp-charras)]

Commit a18c7496 should fix that.
Gerber X2 netlist extension can be now enabled or disabled both in X1 and X2 format.

Please test.