pgsql: Strip file names reported in error messages in vpath builds

Strip file names reported in error messages in vpath builds

In vpath builds, the __FILE__ macro that is used in verbose error
reports contains the full absolute file name, which makes the error
messages excessively verbose.  So keep only the base name, thus
matching the behavior of non-vpath builds.

Branch
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REL8_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/1a44811775d00ac4ac1d3e727bdc9c05ea56a8b9

Modified Files
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src/backend/utils/error/elog.c |   18 ++++++++++++++++--
1 files changed, 16 insertions(+), 2 deletions(-)