Remove the check for COPY TO STDIN and COPY FROM STDOUT from ecpg.

The backend grammar treats STDIN and STDOUT completely interchangeable, so
that the above accepted. Arguably that was a mistake the backend grammar,
but it's not ecpg's business to second guess that.
Install headers from the new src/include/common subdirectory.

This got missed in commit 8396447cdbdff0b62914748de2fec04281dc9114.

Andres Freund
Clean up "stopgap" implementation of timestamptz_to_str().

Use correct type for "result", fix bogus strftime argument, don't use
unnecessary static variables, improve comments.

Andres Freund and Tom Lane
Add missing .gitignore file.