add operator ^= to mean not equal (like != and <>)

Hi everyone, I am doding some jobs in postgres. I want to add "^=" like "!=" and "<>". So i modify the code in scan.l. Plan 1: equals_greater "=>" less_equals "<=" greater_equals ">=" less_greater "<>" not_equals (!=|\^=) Maybe i can delete some code to make the code more simple. Plan 2: equals

use-regular-expressions-to-simplify-less_greater-and-not_equals.patch

we can use regular expressions (<>|!=) to cover "<>" and "!=". There is no need to have two definitions less_greater and not_equals, because it will confuse developer. So, we can use only not_equals to cover this operator set. Please review my patch. Thanks. use-regular-expressions-to-simp