#640 build boost regex from Boost 1.57.0 source

[Robert Pyron]

Changes to allow build of boost regex from Boost 1.57.0 source. Some important files have changed location within the Boost source tree.

This patch uses "SETLOCAL EnableDelayedExpansion"; I don't know the minimum version of Windows for this to work.

[Robert Pyron]

• SETLOCAL ENABLEDELAYEDEXPANSION is available at least since Windows XP, but may require changing a registry setting. I have no way to try this.
• From http://ss64.com/nt/delayedexpansion.html, "One downside of DelayedExpansion is that processing a file with a ! in the filename will be interpreted as a variable, this is not a common occurence, but it can cause scripts to fail".