Fix infinite loop on bad literal data

Returning true here just puts us in an infinite loop, not sure what was supposed to happen?

Fixes icsharpcode#229.

src/ICSharpCode.SharpZipLib/Zip/Compression/Inflater.cs

@@ -273,7 +273,8 @@ private bool DecodeHuffman()
 						while (((symbol = litlenTree.GetSymbol(input)) & ~0xff) == 0) {
 							outputWindow.Write(symbol);
 							if (--free < 258) {
-								return true;
+								// If this happens we will be stuck in an infinite loop.
+								throw new SharpZipBaseException("Literal symbol count exceeds window size, input file may be corrupt.");
 							}
 						}