[GRASS5] fixed lot's of compiler warnings

[Markus Neteler]

Hi,

as the subject says (valid for GRASS 6.1-CVS). This hopefully
improves the gcc4 and Fedora4 readiness...

Still todo for someone else:
 lib/display
 imagery/i.class
 imagery/i.ortho.photo/photo.2target
 imagery/i.ortho.photo/photo.2image
 imagery/i.points
 imagery/i.vpoints

All of them have this error (I dunno how to fix that):
 zoom_box.c:5: error: 'y1' redeclared as different kind of symbol
 zoom_box.c:5: error: 'y1' redeclared as different kind of symbol


Also remaining (too complicated for me):
 raster/r.kappa
 raster/r.random.cells
 raster/r.random.surface
 raster/wildfire/r.ros
 raster/wildfire/r.spread
 raster/wildfire/r.spreadpath
 raster3d/r3.mask
 raster3d/r3.mkdspf
 visualization/nviz
 visualization/xganim

Cheers

 markus