pgsql: Fix an ancient typo that prevented the detection of conflicting

Log Message:
-----------
Fix an ancient typo that prevented the detection of conflicting fields when
interval input "invalid" was specified together with other fields.  Spotted
by Neil Conway with the help of a clang warning.  Although this has been
wrong since the interval code was written more than 10 years ago, it doesn't
affect anything beyond which error message you get for a wrong input, so not
worth back-patching very far.

Modified Files:
--------------
    pgsql/src/backend/utils/adt:
        datetime.c (r1.212 -> r1.213)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/datetime.c?r1=1.212&r2=1.213)
    pgsql/src/interfaces/ecpg/pgtypeslib:
        interval.c (r1.42 -> r1.43)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/pgtypeslib/interval.c?r1=1.42&r2=1.43)