st_OffsetCurve bug for geometries where St_IsSimple return false

[francob]

version "POSTGIS="2.1.0 r11822" GEOS="3.4.2-CAPI-1.8.2 r3921"

st_OffsetCurve doesnt' work for geometries where St_IsSimple return false.

Example:

geom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

SELECT st_OffsetCurve(geom,10)

return ERROR: GEOSOffsetCurve: TopologyException: assigned depths do not match at 1512895.9378084207 5033276.5839699283

SELECT st_OffsetCurve(st_SimplifyPreserveTopology((geom),0.6),10)

return (same error) ERROR: GEOSOffsetCurve: TopologyException: assigned depths do not match at 1512895.9378084207 5033276.5839699283

SELECT st_OffsetCurve(st_SimplifyPreserveTopology((geom),0.7),10)

works

If you need I have more sxample geometries

[komzpa]

In 16409:

Format lwgeom_geos_clean.c before digging in

References #2508

[komzpa]

In 16444:

ST_OffsetCurve: support for MULTILINESTRING, GEOMETRYCOLLECTION and non-simple inputs

Closes #2508
Closes ​https://github.com/postgis/postgis/pull/224

[komzpa]

In 16445:

ST_OffsetCurve: update docs about MULTI*

References #2508