progress: check for ui.quiet and ui.debugflag before we write ui.quiet and ui.debugflag are not initialized during uisetup and reposetup. progressui is always initialized, therefore we have to check during write() if ui.quiet is set or not.

changelog: handle decoding of NULs in extra more carefully (issue3156) Escaped NULs adjacent to [0-7] could be decoded as octal. This hits about 0.24% of changesets with transplant, which stores binary nodes.