Dollar quoting ($$) and single quoting (') errors when populating PostgreSQL dumps

[YasserHassan]

The error Syntax error: 7 ERROR: unterminated dollar-quoted string at or near "$$ (reported in #1128) that was fixed in #1450 seems did not account for all cases. It works when the dollar quoting is at the beginning of the line like this:

...
    AS
$$
    BEGIN
...

but produces the mentioned error when the same code above is written like below, which is generated by pg_dump and is a valid syntax as shown in the examples at CREATE FUNCTION:

...
    AS $$
    BEGIN
...

Also it does not work at all with the following quoting variations:

• Dollar quoting with a tag such as $BODY$.
• Single quoting instead of dollar quoting as produced by the '--disable-dollar-quoting' pg_dump option.

I tested that on version 2.0.16 but by looking into the code of version 2.1.1, it seems it's valid there too.

[DavertMik]

Thanks. Looks like you deeply discovered this issue. Could you send PR for it?
Please send it to 2.1.x branch (or to 2.0 if you still use it)

[YasserHassan]

@DavertMik, done for branch 2.0 for the case when $$ is not at the beginning of the line. Please notice that the tagged dollar quoting (e.g. $function$) and single quoting mentioned above are still unhandled. This fix at least can help when the development database is automatically dumped using `pg_dump' then populated to the testing database before testing.

I suggest adding these two points as known issues and limitations until if/when they are implemented.

[YasserHassan]

@DavertMik could you please review this commit? The testing errors seem irrelevant.