Sort zone order.
Test for 8.0::ADT.struct
Changed a few ADT.struct to Stdio.Buffer
Stdio.Buffer instead of ADT.struct
Fixed speed of bignum and 64bit integer encoding in encode_value

This fixes an issue we ran into in one of our servers where encoding a
reasonably sized list of crc32 hashes (unsigned 32 bit integers, so
50% would not fit in a signed 32bit integer) took 10+ seconds.

| Pike v8.1 release 0 running Hilfe v3.5 (Incremental Pike Frontend)
| > array ints = allocate(50000,random)(1<<32);
| > array bigs = allocate(50000,random)(1<<320);
| > set format bench

Before my fix:
| > encode_value(ints),0;  ... Execution: 1.24s
| > encode_value(bigs),0;  ... Execution: 121.31ms

After my fix:
| > encode_value(ints),0; ... Execution: 18.58ms
| > encode_value(b),0;    ... Execution: 43.85ms

So. "normal" 64 bit integers are now encoded about 66 times faster.
Actual bignums are only 3x faster.

This makes me somewhat suspicious about the speed of various bignum
functions in pike, by the way, since the only thing that should really
have been done is to remove the function call + object
creation/destruction overhead.

And it does not take even close to 1.2 seconds to create and free
50.000 bignum objects (creating and reallocating the array 'b' above
takes about 50ms).
pgsql: reconnect robustness improved.
Image.SVG: Use features in RSVG 2.14 and later.

Many of the APIs that were used in the Image.SVG module have been
deprecated by more modern APIs. Most of the relevant new APIs
were added in RSVG 2.14.

With RSVG 2.14 and later SVGs are now rendered and scaled with Cairo.

Fixes all known compilation warnings for the Image.SVG module.
pgsql: Rebalance threads, cut away some fat and unnecessary mutexes.

The benchmark performance is now within spitting distance of the
old pgsql driver for the unbatched single queries.
For large batches (>20), the new driver beats everyone pants down.
For single batches (==1), the new driver is about 2% slower than
the old 7.8 version.
pgsql: Off-by-one error.