Add pooling discussion.

Author: bmomjian

doc/TODO

@@ -255,6 +255,7 @@ MISC
 * Improve statistics storage in pg_class [performance]
 * Improve VACUUM speed with indexes [vacuum]
 * -BSD/OS does not support locale because there is no LC_MESSAGES (Bruce)
+* Add connection pooling [pool]
 
 SOURCE CODE
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