pgsql: Prevent shutdown in normal mode if online backup is running, and

Log Message:
-----------
Prevent shutdown in normal mode if online backup is running, and
have pg_ctl warn about this.

Cancel running online backups (by renaming the backup_label file,
thus rendering the backup useless) when shutting down in fast mode.

Laurenz Albe

Modified Files:
--------------
pgsql/doc/src/sgml:
runtime.sgml (r1.414 -> r1.415)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml?r1=1.414&r2=1.415)
pgsql/doc/src/sgml/ref:
pg_ctl-ref.sgml (r1.44 -> r1.45)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_ctl-ref.sgml?r1=1.44&r2=1.45)
pgsql/src/backend/access/transam:
xlog.c (r1.298 -> r1.299)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c?r1=1.298&r2=1.299)
pgsql/src/backend/postmaster:
postmaster.c (r1.554 -> r1.555)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c?r1=1.554&r2=1.555)
pgsql/src/bin/pg_ctl:
pg_ctl.c (r1.96 -> r1.97)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_ctl/pg_ctl.c?r1=1.96&r2=1.97)
pgsql/src/include:
miscadmin.h (r1.201 -> r1.202)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/miscadmin.h?r1=1.201&r2=1.202)