Fix array_out's failure to backslash backslashes, per bug# 524. Also,

remove brain-dead rule that double quotes are needed if and only if the
datatype is pass-by-reference; neither direction of the implication holds
water.  Instead, examine the actual data string to see if it contains
any characters that force us to quote it.
Add some documentation about quoting of array values, which was previously
explained nowhere AFAICT.