Replace unused namespace/package header files with a single file

[nila]

26 namespace/package header files have lost general use with GEOS 3.0 and are now with a few exceptions only used for doxygen documentation purpose. These file may be replaced by a single file collecting namespace documentations and concrete includes where still used.

Relevant files: geomgraph.h, geomgraphindex.h, geomPrep.h, geosAlgorithm.h, indexBintree.h, indexChain.h, indexIntervalRTree.h, indexQuadtree.h, indexStrtree.h, indexSweepline.h, io.h, noding.h, nodingSnapround.h, nodingSnapround.h, opBuffer.h, opDistance.h, operation.h, opLinemerge.h, opOverlay.h, opPolygonize.h, opPredicate.h, opRelate.h, opValid.h, planargraph.h, precision.h, spatialIndex.h

[nila]

Pull request ​PR#242 is a suggestion to address this issue.

[nila]

This issue is fixed with [ff80c6d661cd2df4caf06dd8830082e42298d2cf/git] and may be closed.

Thank you @dbaston for ​pointing in this direction.