pgsql: Remove obsolete comment from btbuild() and hashbuild(): we no

Log Message:
-----------
Remove obsolete comment from btbuild() and hashbuild(): we no longer use
a global variable to control building indexes.

Modified Files:
--------------
    pgsql/src/backend/access/hash:
        hash.c (r1.73 -> r1.74)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hash.c.diff?r1=1.73&r2=1.74)
    pgsql/src/backend/access/nbtree:
        nbtree.c (r1.120 -> r1.121)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtree.c.diff?r1=1.120&r2=1.121)