pgsql: Implement streaming xlog for backup tools

Implement streaming xlog for backup tools

Add option for parallel streaming of the transaction log while a
base backup is running, to get the logfiles before the server has
removed them.

Also add a tool called pg_receivexlog, which streams the transaction
log into files, creating a log archive without having to wait for
segments to complete, thus decreasing the window of data loss without
having to waste space using archive_timeout. This works best in
combination with archive_command - suggested usage docs etc coming later.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/d9bae5317300cf983dd9f01cc2e561c0eecd109a

Modified Files
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doc/src/sgml/ref/allfiles.sgml | 1 +
doc/src/sgml/ref/pg_basebackup.sgml | 65 ++++-
doc/src/sgml/ref/pg_receivexlog.sgml | 270 ++++++++++++++++
doc/src/sgml/reference.sgml | 1 +
src/bin/pg_basebackup/.gitignore | 1 +
src/bin/pg_basebackup/Makefile | 15 +-
src/bin/pg_basebackup/pg_basebackup.c | 538 +++++++++++++++++++++++---------
src/bin/pg_basebackup/pg_receivexlog.c | 465 +++++++++++++++++++++++++++
src/bin/pg_basebackup/receivelog.c | 398 +++++++++++++++++++++++
src/bin/pg_basebackup/receivelog.h | 22 ++
src/bin/pg_basebackup/streamutil.c | 165 ++++++++++
src/bin/pg_basebackup/streamutil.h | 22 ++
src/tools/msvc/Mkvcbuild.pm | 7 +
13 files changed, 1805 insertions(+), 165 deletions(-)