pgsql: Revert "Provide DLLEXPORT markers for C functions via PG_FUNCTIO

Revert "Provide DLLEXPORT markers for C functions via PG_FUNCTION_INFO_V1 macro."

This reverts commit c8ead2a3974d3eada145a0e18940150039493cc9.
Seems there is no way to do this that doesn't cause MSVC to give
warnings, so let's just go back to the way we've been doing it.

Discussion: <11843.1478358206@sss.pgh.pa.us>

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/33cb96ba1a84c612491fb5794674a649d1a6a4d6

Modified Files
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contrib/hstore/hstore.h |  2 +-
contrib/ltree/ltree.h   | 40 ++++++++++++++++++++--------------------
doc/src/sgml/xfunc.sgml | 17 -----------------
src/include/fmgr.h      |  7 ++++---
4 files changed, 25 insertions(+), 41 deletions(-)