Added support for the bootfile option in the slirp config file.
Moved slirp config parameters to the ethernet module object.
Added initial documentation for the built-in slirp support


git-svn-id: svn://svn.code.sf.net/p/bochs/code/trunk@12226 6c8e4198-a580-4521-a02f-c9ae86df1db9