#1395 "hostemu" subcommand "EXECIO" bugs

[Erich]

The "hostemu" library's "EXECIO" subcommand shows several issues: mainframe-incompatible return codes, SKIP not accepted as single option, not all combinations of options accepted, illegal stem varibale name not checked, etc.

regression tests should be done, docs should be updated (see also [documentation:#216])

[Erich]

code changes committed with revision [r11143].
new tests committed with revision [r11144].
doc changes committed with revision [r11145].