Currently, only very simple Eshell commands can be run in the 
background. Anything more complicated, such as Eshell script files or 
things involving variable interpolation fail. For example, this should 
print "hi", but it doesn't print anything (aside from messages about the 
processes that started/stopped):

   *echo ${*echo hi} &

The attached patches fix this.

Note: In reality, this is just a preliminary set of changes to add full 
job control to Eshell, but that's more complex. (Hopefully, I'll get 
that working next though.)