pgsql: Update documentation to mention huge pages on other OSes

Update documentation to mention huge pages on other OSes

Previously, the docs implied that only Linux and Windows could use huge
pages.  That's not quite true: it's just that we only know how to
request them explicitly on those OSes.  Be more explicit about what
huge_pages really does and mention that some OSes may use huge pages
automatically.

Author: Thomas Munro and Catalin Iacob
Reviewed-By: Justin Pryzby, Peter Eisentraut
Discussion: https://postgr.es/m/CAEepm=3qzR-hfjepymohuC4XO5phxoSoipOjm6BEhnJHjNR+jg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2a5ecb56d22340a00393fa60e7b910c472071875

Modified Files
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doc/src/sgml/config.sgml | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)