Fix numerous build failures:
    - Build with bundled ipywidgets for now
    - Drop unneeded -givaro patch
    - Lots of new BRs for building documentation
    - R python-backports-shutil_get_terminal_size and python-traitlets (bz 1464520)
    - Fix Singular LIB path
    - Make sure install operates in a UTF-8 environment
    - Build documention with an X server running
    - Build HTML documentation with mathjax