* update to VS2013
* drop support for XP, now at least Vista is required:
  This is only for trunk and the next 1.9 version. The stable branch and all 1.8.x versions still support XP.
* patch apr to fix a linker error with the Windows 8.1 SDK

git-svn-id: http://tortoisesvn.googlecode.com/svn/trunk/src/AsyncFramework@25090 4cfb86a4-2c7a-11df-bd14-c1e331e6ceac