Index update fails on Windows about codesearch HOT 5 OPEN

This may be related - I noticed a number of temp files are not cleaned up on 
the Windows version. This is probably because UnmapViewOfFile does not appear 
to be used, and the handle returned by CreateFileMapping isn't closed. I would 
probably add this info to mmapData and give it a Close() method, which I would 
use right before removing the file.

Hahahaha. I decided to try and fix the bugs in the code to make this work. I'm 
still at it. First, the checked in code doesn't compile out of the box anymore, 
due to a missing typecast. That's just the beginning, though. During a simple 
index update, the code generates about a dozen intermediate/temporary files. 
*None* of them are correctly cleaned up. I'm guessing the only reason any of 
this code works at all on *ix systems is due to the lack of file locking. 
Sadly, the code has almost no error checking performed on critical file system 
operations, and none of the abstractions used for file-system objects (Index, 
IndexWriter) even had the ability to close cleanly - they basically only had 
API to open/read/write, with the assumption that the OS would let you call 
Remove on the open file when you were done.

I've attached a patch that fixes this, plus the compile error. It also changes 
the path used to store the index (e.g. use APPDATA instead of HOME environment 
variable)

Thanks - the patch definitely helps - the search index is updated and renamed 
correctly. Two things though - mmap_linux.go needs a copy of unmmapFile, and 
the temporary files generated as a part of the index process are not deleted.

This patch seems to get the temp files deleted.