pgsql: Allow server-side compression to be used with -Fp.

Allow server-side compression to be used with -Fp.

If you have a low-bandwidth connection between the client and the
server, it's reasonable to want to compress on the server side but
then decompress and extract the backup on the client side. This
commit allows you do to do just that.

Dipesh Pandit, with minor and mostly cosmetic changes by me.

Discussion: http://postgr.es/m/CAN1g5_HiSh8ajUMd4ePtGyCXo89iKZTzaNyzP_qv1eJbi4YHXA@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/d45099425eb19e420433c9d81d354fe585f4dbd6

Modified Files
--------------
doc/src/sgml/ref/pg_basebackup.sgml      |   7 +-
src/bin/pg_basebackup/Makefile           |   1 +
src/bin/pg_basebackup/bbstreamer.h       |   1 +
src/bin/pg_basebackup/bbstreamer_file.c  | 182 ---------------
src/bin/pg_basebackup/bbstreamer_gzip.c  | 380 +++++++++++++++++++++++++++++++
src/bin/pg_basebackup/pg_basebackup.c    |  19 +-
src/bin/pg_verifybackup/t/009_extract.pl |  61 +++++
7 files changed, 463 insertions(+), 188 deletions(-)