Resolving pg_standby -l

Short patch to
1. disable pg_standby -l
    One line change only appropriate for this stage of release
2. Remove mention of -l and link from docs

pg_standby -l is still accepted, just does nothing (for now).

Existing code maintained in case we backpatch a fix for linking problem
at a later date.

--
 Simon Riggs           www.2ndQuadrant.com
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