Made ksh portability changes
Made ksh portability changes

Added specific message for ksh in identifying the proper shell
initialization file.

Changed rbenv functiond definition to be more portable.
Shell functions should be defined by using the function command or
using the parenthesis grammar, but using both is not portable:

rbenv() {...  -or-
function rbenv { ...

mediadoneright/rbenv,cehoffman/rbenv,mediadoneright/rbenv,cehoffman/rbenv,cehoffman/rbenv,mediadoneright/rbenv