ENH: Adding kwsys implementation for a DynamicLoader class. Copy from itkDynamicLoader, with patch from cmDynamicLoader

ENH: Added kwsys::String class to shorten debugging symbols and error messages involving std::string.

BUG: When more than one command is given and one of them fails to start and the rest are killed, do not forget to reap the killed children.

ENH: Improved robustness of sharing parent pipes with children.  This ensures that the parent pipe handles are inherited by the children.  If a parent pipe handle is invalid a handle to an empty pipe is given to the child to make sure all pipes are defined for the children.

BUG: Do not close handle obtained from GetModuleHandle which does not increase the reference count of the module.

ENH: Change flag to PASS_REGULAR_EXPRESSION and FAIL_REGULAR_EXPRESSION and add help in cmSetTestsPropertiesCommand

ENH: Improved file modification time comparison on Windows to use GetFileAttributesEx instead of CreateFile/GetFileTime/CloseHandle to get file times.  This results in a 30% reduction in time to do a build system check.