Doc: Documentation for long-lived graceful restart

	re-establish after a restart before deleting stale routes. Default:

	120 seconds.

	<tag><label id="bgp-long-lived-graceful-restart">long lived graceful restart <m/switch/|aware</tag>

	The long-lived graceful restart is an extension of the traditional

	<ref id="bgp-graceful-restart" name="BGP graceful restart">, where stale

	routes are kept even after the <ref id="bgp-graceful-restart-time"

	name="restart time"> expires for additional long-lived stale time, but

	they are marked with the LLGR_STALE community, depreferenced, and

	withdrawn from routers not supporting LLGR. Like traditional BGP

	graceful restart, it has three states: disabled, aware (receiving-only),

	and enabled. Note that long-lived graceful restart requires at least

	aware level of traditional BGP graceful restart. Default: aware, unless

	graceful restart is disabled.

	<tag><label id="bgp-long-lived-stale-time">long lived stale time <m/number/</tag>

	The long-lived stale time is announced in the BGP long-lived graceful

	restart capability and specifies how long the neighbor would keep stale

	routes depreferenced during long-lived graceful restart until either the

	session is re-stablished and synchronized or the stale time expires and

	routes are removed. Default: 3600 seconds.

	<tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>

	<rfc id="1997"> demands that BGP speaker should process well-known

	communities like no-export (65535, 65281) or no-advertise (65535,