c:xm/1 not mirrored in shell_default.erl

[Ulf Wiger (AL/EAB)]

I noticed the function xm(M) when typing help() in the 
shell. However, calling xm(M) from the shell doesn't 
work. Calling c:xm(M) does.

The problem is that shell_default:xm(M) was never added.

I've not bothered to make a patch, since the needed change
is so obvious (well, there are two alternatives, I guess:
either add it to shell_default, or remove it from c  ;-)

/Uffe