pgsql: Add pg_size_bytes() to parse human-readable size strings.

Add pg_size_bytes() to parse human-readable size strings.

This will parse strings in the format produced by pg_size_pretty() and
return sizes in bytes. This allows queries to be written with clauses
like "pg_total_relation_size(oid) > pg_size_bytes('10 GB')".

Author: Pavel Stehule with various improvements by Vitaly Burovoy
Discussion: http://www.postgresql.org/message-id/CAFj8pRD-tGoDKnxdYgECzA4On01_uRqPrwF-8LdkSE-6bDHp0w@mail.gmail.com
Reviewed-by: Vitaly Burovoy, Oleksandr Shulgin, Kyotaro Horiguchi,
    Michael Paquier and Robert Haas

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/53874c5228fe16589a4d01b3e1fab3678e0fd8e3

Modified Files
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doc/src/sgml/func.sgml               |  32 +++++++-
src/backend/utils/adt/dbsize.c       | 149 +++++++++++++++++++++++++++++++++++
src/include/catalog/catversion.h     |   2 +-
src/include/catalog/pg_proc.h        |   2 +
src/include/utils/builtins.h         |   1 +
src/test/regress/expected/dbsize.out | 109 +++++++++++++++++++++++++
src/test/regress/sql/dbsize.sql      |  39 +++++++++
7 files changed, 331 insertions(+), 3 deletions(-)