Add some missing exports to fast-logger

patching/patches/fast-logger-2.0.2.patch

@@ -0,0 +1,12 @@
+diff -ru orig/System/Log/FastLogger.hs new/System/Log/FastLogger.hs
+--- orig/System/Log/FastLogger.hs	2013-12-24 10:23:27.725895194 +0200
++++ new/System/Log/FastLogger.hs	2013-12-24 10:23:27.000000000 +0200
+@@ -13,6 +13,8 @@
+   -- * Log messages
+   , LogStr
+   , ToLogStr(..)
++  , logStrLength
++  , logStrBuilder
+   -- * Writing a log message
+   , pushLogStr
+   -- * Flushing buffered log messages