[Therion] new Therion 6.0.0

[Therion]

Hi, there is a new release 6.0.0 of Therion.
Release notes:

v6.0.0          Therion 6.0.0 (2021-07-13):
    
    therion:
     * support for colour models: cmyk, rgb, grayscale (see the color-model layout
       option in the Thbook)
     * support for colour management (see the color-profile layout option)
     * support for linear and radial shading (colour gradients) in MetaPost
       (withlinearshading and withradialshading options)
     * support for smooth colour transitions of scrap backgrounds in PDF maps
       if the map-fg is coloured by altitude
     * added smooth-shading <off/quick> layout switch – quick is the default
     * reimplemented internal processing of patterns and transparent colors in
       MetaPost (incompatible changes: the drawing option 'withtransparentcolor',
       macro 'def_transparent_rgb' and predefined transparent colors tr_bg,
       tr_white, tr_black were removed; use the drawing option
       'withcolor <color> withalpha <number>' instead)
     * reimplemented conversion of MetaPost output to PDF
     * support for double number system in MetaPost (this eliminates the current
       MetaPost limits; see the chapter Limitations in the Appendix of the Thbook)
     * tex-refs-registers <on/off> initialization file option added (see the
       chapters Initialization files and Limitations in the Appendix of the Thbook)
     * support for LuaTeX as an alternative to pdfTeX
     * support for relative paths in TeX (\inputrel, \savepath and \loadpicture) and
       in MetaPost (inputrel)
     * updated Serbian translation
     * bugs fixed:
       - symbol-hide,show,color not working for user defined symbols
       - ISO8859-2 literals in the source code caused clang warnings
       - removed unnecessary SOURCE_DATE_EPOCH in the thbook Makefile
       - fixed numerical instability in l_overhang_SKBB
       - swapped anastomosis & karren symbols
       - no station scrap continuation list [#333]
       - fixed arrows flipping [#245]
       - colour preview-above doesn't work [#90]
       - KML export fix [#84]
       - p_smartlabel fails with a picture argument
       - other minor fixes
     * included {fmt} library
     * updated shapelib
    
    loch:
     * Tools→Selection – only displays selected surveys
     * bugs fixed:
       - missing title
       - autorotation issues
    
    infrastructure:
     * support for CMake builds (thanks to Matěj Plch)
     * C++14 required
     * use Github Actions to create Github releases

Best regards,
Therion team