Fix for Boost up to 1.54 which fails to compile with MSVC 2013

git-svn-id: http://amule.googlecode.com/svn/trunk@10815 6ea3b165-b8b8-dda6-0cea-db2f03e7d5ff
Less writing of known files list during hashing (every 3000MB instead of 300) - stoatwblr

Files have become larger and hashing faster.
See http://amule.forumer.com/10814-patch-src-amule-cpp-t2345296.html

git-svn-id: http://amule.googlecode.com/svn/trunk@10816 6ea3b165-b8b8-dda6-0cea-db2f03e7d5ff