pgsql: Avoid compiler warnings due to possibly unused variables

Avoid compiler warnings due to possibly unused variables

gcc 4.6 complains about these because of the new option
-Wunused-but-set-variable which comes in with -Wall, so cast them to
void, which avoids the warning.

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/7357558fc8866e3a449aa9473c419b593d67b5b6

Modified Files
--------------
src/backend/nodes/read.c      |    1 +
src/backend/nodes/readfuncs.c |    3 ++-
2 files changed, 3 insertions(+), 1 deletions(-)