Revert "Signal error for symbol names with strange quotes (Bug#2967)"

Revert "Signal error for symbol names with strange quotes (Bug#2967)"

That commit did not make the corresponding change to printing, thus
breaking the (eq (read (prin1-to-string SYM)) SYM) invariant for those
symbols.  It's too late in the release cycle to change printing
behavior, therefore revert the reader change.

Don't merge to master, the print function will be updated there (see
"Fix round tripping of read->print for symbols with strange quotes").