c++boost.gif -> boost.png replacement

[SVN r25573]

enable_shared_from_this.html

@@ -8,7 +8,7 @@
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-					<img src="../../c++boost.gif" alt="c++boost.gif (8819 bytes)" width="277" height="86">
+					<img src="../../boost.png" alt="boost.png (6897 bytes)" width="277" height="86">
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 					<h1>enable_shared_from_this.hpp</h1>