pgsql: Back-patch fix for renaming asyncCommitLSN to asyncXactLSN.

Log Message:
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Back-patch fix for renaming asyncCommitLSN to asyncXactLSN.
AIUI this was supposed to go into 9.0 as well as HEAD.

Tags:
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REL9_0_STABLE

Modified Files:
--------------
    pgsql/src/backend/access/transam:
        xact.c (r1.293.2.1 -> r1.293.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xact.c?r1=1.293.2.1&r2=1.293.2.2)
        xlog.c (r1.430 -> r1.430.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c?r1=1.430&r2=1.430.2.1)
    pgsql/src/include/access:
        xlog.h (r1.114 -> r1.114.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/access/xlog.h?r1=1.114&r2=1.114.2.1)