Support all whitespaces as delimiter for inside a interval value

 
postgres=# select interval E'1 \t day';
 interval
----------
 1 day
(1 row)

postgres=# select interval E'1\t' day;
 interval
----------
 1 day
(1 row)

postgres=# select interval '1 ' day;
 interval
----------
 1 day
(1 row)

 
We are now able to handle whitespaces for integral and fractional types, and the leading or trailing whitespaces for interval, date, and timestamps. But the current interval parser is not able to identify whitespaces as separates as PostgreSQL can do