pgsql: Reduce per-character overhead in COPY OUT by combining calls to

Log Message:
-----------
Reduce per-character overhead in COPY OUT by combining calls to
CopySendData.

Modified Files:
--------------
pgsql/src/backend/commands:
copy.c (r1.264 -> r1.265)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/copy.c.diff?r1=1.264&r2=1.265)