[crossfire] Create earth wall / earth to dust issue

[Nicolas Weeger (Laposte)]

Hello.

juhaj on IRC reported a earth to dust bug.

Looking at the code, I see 2 issues:
* in server/spell_effect.c, lines 705/706, it should be imo for(i= 
-range;i<=range;i++) instead of for(i= -range;i<range;i++) since we want to 
do [-range..range] inclusive
* earth to dust fails because no object with move_block is on the spot. This 
is because earth wall that was created has no move_block set - wall is alive, 
thus player/monsters can't get on it. I'm not totally sure what's the best 
way to fix that. Maybe spell should have a move_block set?

Nicolas