Added filename cache
Added filename cache

because CleanupInvalidFileNameChars is expensive

bryjamus/NLog,ie-zero/NLog,MoaidHathot/NLog,sean-gilliam/NLog,luigiberrettini/NLog,AndreGleichner/NLog,AndreGleichner/NLog,tetrodoxin/NLog,bjornbouetsmith/NLog,MartinTherriault/NLog,luigiberrettini/NLog,ilya-g/NLog,tohosnet/NLog,NLog/NLog,tetrodoxin/NLog,kevindaub/NLog,littlesmilelove/NLog,littlesmilelove/NLog,michaeljbaird/NLog,nazim9214/NLog,UgurAldanmaz/NLog,bhaeussermann/NLog,tohosnet/NLog,MoaidHathot/NLog,MartinTherriault/NLog,BrutalCode/NLog,ilya-g/NLog,hubo0831/NLog,michaeljbaird/NLog,304NotModified/NLog,kevindaub/NLog,UgurAldanmaz/NLog,nazim9214/NLog,BrutalCode/NLog,breyed/NLog,snakefoot/NLog,ie-zero/NLog,bryjamus/NLog,breyed/NLog,hubo0831/NLog,bjornbouetsmith/NLog,bhaeussermann/NLog