Initial Windows Port

Add SCons support for building wildtiger.lib & wt.exe
- Checked in a special header called os_win_wiredtiger_config.h since scons cannot generate the autotools config.h header

Added:
- os_win directory full of Windows OS versions of WT OS compat layer
- os_windows.h for Windows (windows.h is already reserved by the OS)
- msvc.h for the compiler

In terms of preprocessor defines,
_WIN32 is Windows
_MVC_VER is the Microsoft Visual C compiler

Test framework update will be sent in a separate pull request

I will happy to address any KNF style issues myself. I tried to 

Two hacky changes:
1. err.c - I inlined the ifdefs into this file for Windows
2. filename.c - I also inlined the platform ifdefs into this file

Todos left
- fallocate, and dlopen for standalone dlls
- crc intrinsic support
- complete integration into MongoDB (ie, sort out static vs dlls for zlib & snappy)