pgsql: Fix ill-chosen use of "private" as an argument and struct field

Fix ill-chosen use of "private" as an argument and struct field name.

"private" is a keyword in C++, so this breaks the poorly-enforced policy
that header files should be include-able in C++ code.  Per report from
Craig Ringer and some investigation with cpluspluscheck.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=275411912d96c160547a219cb3223efa3737f90d

Modified Files
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src/backend/utils/fmgr/fmgr.c |    8 ++++----
src/include/fmgr.h            |    2 +-
2 files changed, 5 insertions(+), 5 deletions(-)