pgsql: doc: Rewrite how to get the source code

doc: Rewrite how to get the source code

Instead of hardcoding a specific link, give a general link to the
download section of the web site.  This gives the user more download
options and the sysadmins more flexibility.  Also, the previously
presented link didn't work for devel versions.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/858ef718ba6301b24e245bbe3ecf20aa10cb60a4

Modified Files
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doc/src/sgml/installation.sgml |   14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)