[patch] Add line_merge to GEOS geometries under django.contrib.gis

[psmith]

In the C API of GEOS, GEOSLineMerge returns a new geometry that is the result of having merged contiguous line strings in a geometry collection or multi-line string geometry.

Example:

>>> geomcoll = fromstr('MULTILINESTRING((1 1, 3 3), (3 3, 4 2))')
>>> print geomcoll.line_merge()
LINESTRING(1 1, 3 3, 4 2)

[psmith]

Patch to add line_merge to geos geometries, with test case

[jbronn]

Now in the gis-1.1 mercurial repo, see ​http://geodjango.org/hg/gis-1.1/rev/87b34dce202d.

It is now a merged property that is only available on LineString and MultiLineString instances.

[jbronn]

(In [10131]) Refactored the GEOS interface. Improvements include:

• Geometries now allow list-like manipulation, e.g., can add, insert, delete vertexes (or other geometries in collections) like Python lists. Thanks, Aryeh Leib Taurog.
• Added support for GEOS prepared geometries via prepared property. Prepared geometries significantly speed up certain operations.
• Added support for GEOS cascaded union as MultiPolygon.cascaded_union property.
• Added support for GEOS line merge as merged property on LineString, and MultiLineString geometries. Thanks, Paul Smith.
• No longer use the deprecated C API for serialization to/from WKB and WKT. Now use the GEOS I/O classes, which are now exposed as WKTReader, WKTWriter, WKBReader, and WKBWriter (which supports 3D and SRID inclusion)
• Moved each type of geometry to their own module, eliminating the cluttered geometries.py.
• Internally, all C API methods are explicitly called from a module rather than a star import.

Fixed #9557, #9877, #10222

[Jacob]

Milestone 1.1 deleted