pgsql: Revert behaviour of -x/--xlog to 9.1 semantics

Revert behaviour of -x/--xlog to 9.1 semantics

To replace it, add -X/--xlog-method that allows the specification
of fetch or stream.

Do this to avoid unnecessary backwards-incompatiblity. Spotted and
suggested by Peter Eisentraut.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9af34cdec87d8e60f200ccd5b1b695880412c62b

Modified Files
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doc/src/sgml/ref/pg_basebackup.sgml | 15 +++++++++++++--
src/bin/pg_basebackup/pg_basebackup.c | 29 +++++++++++++++++++++++++----
2 files changed, 38 insertions(+), 6 deletions(-)