The previous approach was to search-and-destroy all \r occurrences
no matter what.  That seems more likely to hide bugs than anything
else; indeed it seems to be hiding one now.  Fix things so that
we only transform \r\n to \n.

Side effects: must do this before, not after, chomp'ing if we're
going to chomp, else we'd fail to clean up a trailing \r\n.  Also,
remove safe_psql's redundant repetition of what psql already did;
else it might reduce \r\r\n to \n, which is exactly the scenario
I'm hoping to expose.

Perhaps this should be back-patched, but for now I'm content to
see what happens in HEAD.

Discussion: https://postgr.es/m/412ae8da-76bb-640f-039a-f3513499e53d@gmx.net