pgsql: In HS, Startup process sets SIGALRM when waiting for buffer pin.

Log Message:
-----------
In HS, Startup process sets SIGALRM when waiting for buffer pin. If
woken by alarm we send SIGUSR1 to all backends requesting that they
check to see if they are blocking Startup process. If so, they throw
ERROR/FATAL as for other conflict resolutions. Deadlock stop gap
removed. max_standby_delay = -1 option removed to prevent deadlock.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        backup.sgml (r2.136 -> r2.137)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/backup.sgml?r1=2.136&r2=2.137)
        config.sgml (r1.244 -> r1.245)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.244&r2=1.245)
    pgsql/src/backend/access/transam:
        xlog.c (r1.359 -> r1.360)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c?r1=1.359&r2=1.360)
    pgsql/src/backend/storage/buffer:
        bufmgr.c (r1.254 -> r1.255)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/buffer/bufmgr.c?r1=1.254&r2=1.255)
    pgsql/src/backend/storage/ipc:
        procarray.c (r1.58 -> r1.59)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/procarray.c?r1=1.58&r2=1.59)
        procsignal.c (r1.3 -> r1.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/procsignal.c?r1=1.3&r2=1.4)
        standby.c (r1.6 -> r1.7)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/standby.c?r1=1.6&r2=1.7)
    pgsql/src/backend/storage/lmgr:
        lock.c (r1.190 -> r1.191)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/lock.c?r1=1.190&r2=1.191)
        proc.c (r1.213 -> r1.214)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/proc.c?r1=1.213&r2=1.214)
    pgsql/src/backend/tcop:
        postgres.c (r1.585 -> r1.586)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c?r1=1.585&r2=1.586)
    pgsql/src/backend/utils/misc:
        guc.c (r1.533 -> r1.534)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.533&r2=1.534)
    pgsql/src/include/storage:
        bufmgr.h (r1.123 -> r1.124)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/bufmgr.h?r1=1.123&r2=1.124)
        proc.h (r1.118 -> r1.119)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/proc.h?r1=1.118&r2=1.119)
        procarray.h (r1.30 -> r1.31)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/procarray.h?r1=1.30&r2=1.31)
        procsignal.h (r1.3 -> r1.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/procsignal.h?r1=1.3&r2=1.4)
        standby.h (r1.4 -> r1.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/standby.h?r1=1.4&r2=1.5)