DOC: linux update prerequisites

Document Linux update prerequisites in :

• TXM Manual
• SF README : 0.7.5 and 0.7.6
• Linux setups end page

(from redmine: issue id 1013, created on 2014/09/17 by Matthieu Decorde)

• Relations:
  • parent #967 (closed)

added type::doc type::task + 1 deleted label

changed milestone to %TXM 0.8.2

the documentation have been updated

(from redmine: written on 2021/03/12 by Matthieu Decorde)

closed