Keep a space between a decimal integer literal and a following dot

[makenowjust]

Fixes #419.

[apstndb]

FYI: the official GoogleSQL parenthesize IntLiteral of LHS of DotIdentifier expression when unparsing.

$ execute_query --mode=parse,unparse --sql_mode expression '1 .A'
DotIdentifier [0-4]
  IntLiteral(1) [0-1]
  Identifier(A) [3-4]

(1).A

[makenowjust]

@apstndb I know it, and my fix is intentional because memefish has ParenExpr so the GoogleSQL solution modifies the AST structure.