pgsql: Add PQlibVersion() function to libpq

Add PQlibVersion() function to libpq

This function is like the PQserverVersion() function except
it returns the version of libpq, making it possible for a client
program or driver to determine which version of libpq is in
use at runtime, and not just at link time.

Suggested by Harald Armin Massa and several others.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=de9a4c27fefcc0d104bc9c97f4a93a49a25bf66d

Modified Files
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doc/src/sgml/libpq.sgml | 44 ++++++++++++++++++++++++++++++++++++++
src/interfaces/libpq/exports.txt | 1 +
src/interfaces/libpq/fe-misc.c | 8 +++++++
src/interfaces/libpq/libpq-fe.h | 3 ++
4 files changed, 56 insertions(+), 0 deletions(-)