Format.

Emergency. `blob::read(vector)` was broken!

This traditional `read()` method on `blob`, for compilers that don't
support `std::span`, did not read any data at all.  It just returned the
buffer you gave it.

Fix spelling error(s) (jtv#445)

* Fix spelling error

* Fix another spelling error

Work around broken `<thread>` in MinGW.

Fixes jtv#336, jtv#398, jtv#424, jtv#441

For years now, MinGW has had trouble compiling files which
`#include <thread>`.  The exact errors seem to have evolved over that
time, but MinGW users still can't compile libpqxx without editing the
standard header.

Luckily we don't use this header much yet.  It's just `sleep_for()`.  We
used to have our own function for this, which would use one of a bunch
of platform-specific alternatives.  I basically revived it, except that
`sleep_for` is in `std` and most compilers implement it, so it's
basically MinGW versus everyone else.  And therefore, we really only
need the one alternate implementation.

Add missing includes which broke macOS clang build.

Should help with jtv#416, but I have a feeling this may not be the whole
story.  One step at a time.

Polish.

Removed some old `tools/` scripts.

Re-re-reformat on Ubuntu 20.10.

Fix incorrect `query` & SQLSTATE params in exceptions.

Fixes jtv#378.

Some exception types were being constructed wrong, so instead of the query text they received their SQLSTATE string (and no actual SQLSTATE string).

Rename `to_composite` to `composite_to`.

As per discussion in jtv#355.