Possible lost of file handles in tile / shapefile layer if mapserver encounter an error rendering them.

[arovira@…]

I found several errors in mapshape.c that can compromise mapscript
servers when there is corrupt data:

In function msSHPOpen() if there is an error opening .shx file 
the .shp file is not closed.

In function msSHPOpenFile() if there is an error opening .dbf file
the .shp and .shx files are not closed.

When in a tiled shapefile msSHPWhichShapes() returns MS_DONE (this can occur if 
the reported tileindex shapefile extension is diferent from the tiled shapefile)
the shapefile is left open.