Fix ecpg parsing of sizeof().

The last fix used the wrong non-terminal to define valid types.
More improvement to comment parsing in ecpg.

ECPG is not supposed to allow and output nested comments in C. These comments
are only allowed in the SQL parts and must not be written into the C file.
Also the different handling of different comments is documented.
Change SET LOCAL/CONSTRAINTS/TRANSACTION and ABORT behavior

Change SET LOCAL/CONSTRAINTS/TRANSACTION behavior outside of a
transaction block from error (post-9.3) to warning.  (Was nothing in <=
9.3.)  Also change ABORT outside of a transaction block from notice to
warning.
Add missing entry for session_preload_libraries in sample config.

The omission was apparently an oversight in the original patch.
Handle domains over arrays like plain arrays in PL/python.

Domains over arrays are now converted to/from python lists when passed as
arguments or return values. Like regular arrays.

This has some potential to break applications that rely on the old behavior
that they are passed as strings, but in practice there probably aren't many
such applications out there.

Rodolfo Campero
ECPG: Make the preprocessor emit ';' if the variable type for a list of
variables is varchar. This fixes this test case:

int main(void)
{
    exec sql begin declare section;
    varchar a[50], b[50];
    exec sql end declare section;

    return 0;
}

Since varchars are internally turned into custom structs and
the type name is emitted for these variable declarations,
the preprocessed code previously had:

struct varchar_1  { ... }  a _,_  struct varchar_2  { ... }  b ;

The comma in the generated C file was a syntax error.

There are no regression test changes since it's not exercised.

Patch by Boszormenyi Zoltan <zb@cybertec.at>
ECPG: Free the malloc()'ed variables in the test so it comes out clean on
Valgrind runs.

Patch by Boszormenyi Zoltan <zb@cybertec.at>
ECPG: Add EXEC SQL CLOSE C to the tests.

Patch by Boszormenyi Zoltan <zb@cybertec.at>
ECPG: Simplify free_variable()

Patch by Boszormenyi Zoltan <zb@cybertec.at>
ECPG: Fix offset to NULL/size indicator array.

Patch by Boszormenyi Zoltan <zb@cybertec.at>
Oops, forgot to "git add" last minute changes to regression test.