ENH: Set CMake Policy CMP0003 to NEW behavior to build without warnings with the upcoming CMake 2.6 release.

COMP: Avoid warning in kwsys IOStream.cxx when the helper functions are not needed.  Define one public symbol to avoid complaints from archivers about empty object files.

STYLE: Remove references to std:: inside KWSys, even in comments.  This will allow a commit check to be added.

BUG: Make sure search paths never have double-slashes.  Leading with two slashes (//) on cygwin looks like a network path and delays while waiting for a non-existent machine.

ENH: Improved escaping in kwsys/System.  Added escape of % for NMake.  Added escape of ; for the VS IDE.

ENH: Add SystemTools::SplitPathRootComponent and re-implement SplitPath to use it.  Add better treatment of user home directory paths.