Prevent infinity and NaN in jsonb/plperl transform

Prevent infinity and NaN in jsonb/plperl transform

jsonb uses numeric internally, and numeric can store NaN, but that is
not allowed by jsonb on input, so we shouldn't store it.  Also prevent
infinity to get a consistent error message.  (numeric input would reject
infinity anyway.)

Reported-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>