do not commit during sage -sdist
move updating of version number to separate script
source version information in sage -sdist
updated sdist documentation
fix including gcc tarball in sdist
prune the sdist repo
use the narrower NO_MSGFMT instead of NO_GETTEXT
Merge branch 't/15401/git_without_gettext' into develop
Merge branch 't/15472/sdist_fixes' into develop