pg_basebackup: Avoid unclean failure with server-compression and -D -.

pg_basebackup: Avoid unclean failure with server-compression and -D -.

Fail with a suitable error message instead. We can't inject the backup
manifest into the output tarfile without decompressing it, and if
we did that, we'd have to recompress the tarfile afterwards to produce
the result the user is expecting. While we have enough infrastructure
in pg_basebackup now to accomplish that whole series of steps without
much additional code, it seems like excessively surprising behavior.
The user probably did not select server-side compression with the idea
that the client was going to end up decompressing it and then
recompressing.

Report from Justin Pryzby. Fix by me.

Discussion: http://postgr.es/m/CA+Tgmob6Rnjz-Qv32h3yJn8nnUkLhrtQDAS4y5AtsgtorAFHRA@mail.gmail.com