4.0 conversion note -- 12-90 dks

v.prune:

cmd version source   = v.prune.c
inter version source = prune.c


misc. changes fr0m 3.2:

1. changed struct head in v.prune.c to dig_head

2. ***type_double doesn't complain about non-double answer??

3. changed call to find_file2 to find_vector2

4. added a check to see if *in_name or *out_name was empty (since
	 the new parser will accept empty arguments

5. fixed bug in fatal_error message when dig src file isn't found

