Introduce std::source_location. (#702)

Introduce `std::source_location`.

Allow exceptions to track source locations.  This is still pretty
rudimentary.

One thing I'm not happy about is the way different exception classes
have their own `source_location` members that are not related to each
other.  This means that if you want to access that field, you have to
catch a fairly specific exception type.

Also of course, it's not great that we can't assume that the compiler
actually supports this feature.  The testing helpers could be much nicer
if they could rely on `source_location` — we might even get by without
some of the preprocessor macros.

NEWS

@@ -31,9 +31,8 @@
  - Support for `PQinitOpenSSL()`. (#678)
  - Slightly more helpful error for unsupported conversions. (#695)
  - Replace some C++ feature tests with C++20 feature macros.
- - Give `stream_to` a move constructor. (#706)
- - Support move in `stream_to`. (#706)
->>>>>>> 42a46214 (Support move assignment as well.)
+ - Support moving of `stream_to`. (#706)
+ - Incorporate `source_location` in exceptions.
 7.7.4
  - `transaction_base::for_each()` is now called `for_stream()`. (#580)
  - New `transaction_base::for_query()` is similar, but non-streaming. (#580)

config/Makefile.in

@@ -123,7 +123,7 @@ am__can_run_installinfo = \
   esac
 am__tagged_files = $(HEADERS) $(SOURCES) $(TAGS_FILES) $(LISP)
 am__DIST_COMMON = $(srcdir)/Makefile.in compile config.guess \
-	config.sub install-sh ltmain.sh missing mkinstalldirs
+	config.sub depcomp install-sh ltmain.sh missing mkinstalldirs
 DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)
 ACLOCAL = @ACLOCAL@
 AMTAR = @AMTAR@