Add possibility to merge lines without changing order of points.

[evgen]

There is a great function ST_LineMerge. But it could reverse lines in multiline to connect them. E.g.

` SELECT ST_AsText(ST_LineMerge( ST_GeomFromText('MULTILINESTRING((-29 -27,1 2),(-29 -27,-45 -33),(-45 -33,-46 -32))')) ); ` returns LINESTRING(1 2,-29 -27,-45 -33,-46 -32) but it could be MULTILINESTRING((-29 -27,1 2),(-29 -27,-45 -33,-46 -32))'.

I process one way roads. When I merge them I'd like to keep point order to know original direction of that segments.

[pramsey]

This seems unlikely to happen (when directions of merged lines disagree then...?) It's also something that can be reported upstream in the JTS repository. If there's interest there, or it's easy, it will eventually flow downstream to here.

[komzpa]

This is actual and needed in generating maps with one-way roads. If directions disagree don't merge.

[robe]

Slating for 3.2.0 as it sounds like a behavior change rather than a bug. Might even need to go to 3.3.0 if we need to introduce a new arg.

[mdavis]

Logged as ​JTS-773.

This is a worthwhile enhancement to JTS and GEOS. It could be exposed in PostGIS as an option to ST_LineMerge.

[robe]

git hub related pull request - ​https://github.com/postgis/postgis/pull/688

[robe]

duplicates #5161