Support mmap-ing dynamic data on win32

[GoogleCodeExporter]

As described in issue 19, the current implementation of dynamic data won't work 
in windows because it relies on:
 * from sys/mman.h: mmap(), munmap()
 * from unistd.h: close()

These header files don't exist in vanilla win32 build environments, so 
compatibility is broken. The fix for close() is being implemented in issue 19, 
but the fix for mmap() is less straightforward.

Original issue reported on code.google.com by [email protected] on 13 Aug 2014 at 11:40