Convert fast/multicol/float-avoidance to reftest.

LayoutTests/platform/mac/fast/multicol/vertical-lr/float-avoidance-expected.txt

Index: LayoutTests/platform/mac/fast/multicol/vertical-lr/float-avoidance-expected.txt
diff --git a/LayoutTests/platform/mac/fast/multicol/vertical-lr/float-avoidance-expected.txt b/LayoutTests/platform/mac/fast/multicol/vertical-lr/float-avoidance-expected.txt
deleted file mode 100644
index 96cfdb52b3049487a67bef0ebcfe86c5d6979560..0000000000000000000000000000000000000000
--- a/LayoutTests/platform/mac/fast/multicol/vertical-lr/float-avoidance-expected.txt
+++ /dev/null
@@ -1,18 +0,0 @@
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-      RenderBlock (floating) {DIV} at (0,0) size 100x200 [bgcolor=#00FF00]
-layer at (108,8) size 132x435
-  RenderBlock {DIV} at (100,0) size 132x435 [border: (10px solid #000000)]
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-      RenderText {#text} at (0,0) size 80x415
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-        text run at (16,56) width 359: "is a sign of things to come from Mozilla. Powerful yet"
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-        text run at (48,245) width 169: "changes to the Extension"
-        text run at (64,0) width 206: "System and icon improvements."