bash-completion functions should be prefixed with __bash_completion__ to stop them conflicting with commands

[Simon Arlott]

All of the functions defined in the /usr/share/bash-completion/completions/* files end up in the shell's global function namespace.

This causes them override lookups for commands in $PATH, which means that any command starting with an underscore is at risk of being overridden by a completions script.

This caused my $HOME/bin/_ssh script to stop being called after the /usr/share/bash-completion/completions/ssh was loaded. The _ssh function was being called instead of my script.

If the function names were prefixed with __bash_completion__ then they would be less likely to conflict with any real commands or user defined functions in a user profile file.