Raster images are not searched relative to the tileindex

[tpievila@…]

If the tileindex is in a subfolder of SHAPEPATH, MS doesn't search for the
images in the subfolder but relative to the SHAPEPATH-folder.
Example: SHAPEPATH=data, TILEINDEX=data/rasters/index.shp. The images will not
be found if they are in data/rasters if the tileindex shape says they are in the
same folder (they need to be in data/).

[fwarmerdam]

Bumping to 4.10 milestone.  I will try and reproduce and possibly fix. 

[fwarmerdam]

Danmo raises the point that this behavior is the same for vectors and is
essentially the intended behavior. 

For 4.10 we should fix the documentation and contemplate latering the 
way this works in 5.0 (but also ensuring that the vector side is consistent). 

[fwarmerdam]

I have reviewed the tileindex code in mapraster.c, and in mapshape.c, and
it seems that it was never "intended" that the files in a tileindex be
found relative to the tileindex.  I find this counter-intuitive but I
am hesitant to change it, especially this close to the 4.10 release. 

(I have not reviewed the OGR tileindex support to see if it matches the
raster and shapefile tileindex behavior)

I have updated the mapfile reference, and the raster howto to make the
path handling for tileindex files more clear.