some HideInComments should not be single line
some HideInComments should not be single line

- ones that appear in expression position should always be multi-line,
  since otherwise the rest of the code on the line will be in comments.
  see e.g. tests/objects-2/test-06.is.html
- so only inserted statements should be possibly made single line
- added a flag to HideInComments to choose between these two modes

UCSD-PL/impscript,UCSD-PL/impscript,UCSD-PL/impscript