#438 Improve HostEmu by removing need for quoting file name

[LesK]

Justification: Rexx is supposed to be easy to 'use' and this is an
unnecessary complication for users of EXECIO.

EXECIO has a formal syntax on VM and the only time I can imagine
that quotes would be needed is when the file name contains a left
parentheses, to distinguish it from the start of the options.

[Bruce]

I have a few questions about this proposed change.
1. What if the file name contains spaces, wouldn't it need to be quoted?
2. On case sensitive/case preserving file systems would the filename be preserved, or would it be up-cased?
3. Wouldn't this change make execio the opposite of all the other i/o BIFs (charin, charout, linein, lineout)?

[Bruce]

An observation. On the mainframe, TSO/E REXX, EXECIO doesn't use file names, but DDNAME. This is similar to the current practice of assigning the filename to a variable, and then using that variable (unquoted) in an EXECIO statement.

From my perspective, the current syntax is in line with both with the stream i/o functions, and with mainframe (MVS, z/OS) REXX usage.