COALESCE returns maximum of available CHAR capacity.

[stanilovsky evgeny]

hi community !
I found that COALESCE('a', 'bb') will return 'a ' <-- whitespace is  
present, i found that now it expands for maximum presented CHAR  
(RelDataType#inferReturnType logic)
sql 92 standard tolds:
'''
COALESCE (V1, V2) is equivalent to the following <case specification>:
CASE WHEN V1 IS NOT NULL THEN V1 ELSE V2 END
'''

So i suppose that existing behavior is erroneous, if it`s ok i fell the  
ticket.

wdyt ?