pgsql: Avoid memcpy() with same source and destination address.

Avoid memcpy() with same source and destination address.

The behavior of that is undefined, although unlikely to lead to problems in
practice.

Found by running regression tests with Valgrind.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/ad7b48ea08d6c33bae0a33c5f2a06272293c0f2f

Modified Files
--------------
src/backend/tsearch/dict_ispell.c |    9 ++++-----
src/backend/utils/adt/tsvector.c  |    3 ++-
2 files changed, 6 insertions(+), 6 deletions(-)