pgsql: Use a consistent error message style for user mappings.

Use a consistent error message style for user mappings.

User mappings are essentially anonymous, so messages referring to "user
mapping foo on server bar" are wrong, and inconsistent with other error
messages referring to user mappings. To be consistent with existing use,
use "user mapping for foo on server bar" instead.

I dropped the noise word "user" from the original suggestion to be
consistent with other uses.

Discussion: http://postgr.es/m/56c6f8ab-b2d6-f1fa-deb0-1d18cf67f7b9@2ndQuadrant.com

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/839cb0649a9f595a8534cdf14afbe89efb1757b1

Modified Files
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src/backend/commands/foreigncmds.c | 8 ++++----
src/test/regress/expected/foreign_data.out | 8 ++++----
2 files changed, 8 insertions(+), 8 deletions(-)