pgsql: Improve comments for AdjustIntervalForTypmod.

Log Message:
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Improve comments for AdjustIntervalForTypmod.

Blank line adjustments.

Modified Files:
--------------
    pgsql/src/backend/utils/adt:
        nabstime.c (r1.134 -> r1.135)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/nabstime.c.diff?r1=1.134&r2=1.135)
        selfuncs.c (r1.183 -> r1.184)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/selfuncs.c.diff?r1=1.183&r2=1.184)
        timestamp.c (r1.131 -> r1.132)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/timestamp.c.diff?r1=1.131&r2=1.132)
    pgsql/src/interfaces/ecpg/pgtypeslib:
        dt_common.c (r1.24 -> r1.25)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/pgtypeslib/dt_common.c.diff?r1=1.24&r2=1.25)
        interval.c (r1.22 -> r1.23)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/pgtypeslib/interval.c.diff?r1=1.22&r2=1.23)
        timestamp.c (r1.26 -> r1.27)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/pgtypeslib/timestamp.c.diff?r1=1.26&r2=1.27)