Remove SVN revision thing on release versions, but keep on dev versions

[robe]

Before we had this annoying

SVN Revision ( )

Which somehow got even more annoying cause the SVN revision number didn't show.

I've taken out of the script for now.

So the generated PDF and html no longer have it.

So 2.3.6, and 2.4.3 built now don't have it.

I was thinking it would still be nice to have it for dev versions.

Perhaps have both the revision number and git hash.

[robe]

okay for 2.5.0dev (trunk) I made the change to have: git log -1 —pretty=format:%ct

Until we come up with something better

Can see it here:

​http://postgis.net/docs/manual-dev/

[robe]

In 16314:

flip version to 2.3.7dev, add in 2.3.6 to upgrade path
backport changes to stamp timestamp
References #3991 for PostGIS 2.3.7dev

[robe]

In 16315:

flip version to 2.4.4dev, add 2.4.3 to upgrade versions
add timestamp to dev docs
closes #3991 for PostGIS 2.4.4dev