pgsql: Improve the error message when creating an empty range partition

Improve the error message when creating an empty range partition.

The previous message didn't mention the name of the table or the
bounds. Put the table name in the primary error message and the
bounds in the detail message.

Amit Langote, changed slightly by me. Suggestions on the exac
phrasing from Tom Lane, David G. Johnston, and Dean Rasheed.

Discussion: http://postgr.es/m/CA+Tgmoae6bpwVa-1BMaVcwvCCeOoJ5B9Q9-RHWo-1gJxfPBZ5Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bb5d6e80b1387f0de58e55ac8e882f68ec6d4fcf

Modified Files
--------------
src/backend/catalog/partition.c | 10 +++-
src/backend/utils/adt/ruleutils.c | 84 +++++++++++++++---------------
src/include/utils/ruleutils.h | 1 +
src/test/regress/expected/create_table.out | 6 ++-
4 files changed, 56 insertions(+), 45 deletions(-)