Refactor additional messages for new monsters spawning.

Not sure why do we need both these and "comes into view".

This includes simplification of:
* shoving the player out of stairs
* "wandering" monsters spawning on the stairs
* fancy messages for in-LOS abyss spawns

For the last part, they had really obscure probabilities, this commit makes
them easier to read.  Also, it avoid mallocs and RNG calls, but that's a
rather negligible optimization.

This commit eliminates a mysterious call to viewwindow() as well.  A comment
claimed that "Special case: must update the view for monsters created in
player LOS." yet this was not done for band members.  It appears removing
that call has no ill effects, but I might have missed something.

1 files changed, 2 insertions, 0 deletions

diff --git a/crawl-ref/source/random.h b/crawl-ref/source/random.h
index f5d04ab49d..b7964d4db3 100644
--- a/crawl-ref/source/random.h
+++ b/crawl-ref/source/random.h
@@ -92,6 +92,8 @@ T random_choose_weighted(int weight, T first, ...)
     return chosen;
 }
 
+const char* random_choose_weighted(int weight, const char* first, ...);
+
 struct dice_def
 {
     int num;