pgsql: Improve documentation about use of Linux huge pages.

Improve documentation about use of Linux huge pages.

Show how to get the system's huge page size, rather than misleadingly
referring to PAGE_SIZE (which is usually understood to be the regular
page size).  Show how to confirm whether huge pages have been allocated.
Minor wordsmithing.  Back-patch to 9.4 where this section appeared.

Branch
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REL9_6_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/dc04be21d655c06ead19247c0240c684ce03b9d1

Modified Files
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doc/src/sgml/runtime.sgml | 62 +++++++++++++++++++++++++++++------------------
1 file changed, 38 insertions(+), 24 deletions(-)