Fixed .NET2 Release build
Fixed .NET2 Release build

The .NET2 project only built in Debug configuration due to not including
the compilation symbol NET2 in the Release configuration.

adamhathcock/sharpcompress,Gert-Jan/sharpcompress,Wagnerp/sharpcompress,adamhathcock/sharpcompress,ycaihua/sharpcompress,Icenium/sharpcompress,tablesmit/sharpcompress,weltkante/sharpcompress,KOLANICH/sharpcompress,adamhathcock/sharpcompress,RainsSoft/sharpcompress,majorsilence/sharpcompress,catester/sharpcompress,sepehr1014/sharpcompress