Update Makefile, discard "linereader" and use "xargs" instead

[waterschen]

Well, my new XCODE_SDK is 10.09 & 10.10, maybe we should find a more elegant way to define it... As i see it, the "linereader" class is unnecessary and makes code complicated. In fact, "xargs" works quite well and is pretty and simple. What do you think?

[emptyhua]

xargs will work slow while a directory contain large number of files，it will fork pinyinmatch too frequently.