ENH: Added SetPipeFile method to allow the process pipeline stdin, stdout, and stderr to be redirected from/to files.

ENH: Removed pipe selection argument from WaitForData method in kwsysProcess.  This greatly simplifies its use.

BUG: Process startup-info struct dwFlags were being set incorrectly due to a change in statement order.

ERR: Some platforms define stdin, stdout, and stderr as macros.  Renaming these symbols to StdIn, StdOut, and StdErr.

ENH: Merged changes from KWSys-MultiProcess-bp to KWSys-MultiProcess-b2t-1-mp to main tree.  This introduces support for process pipelines.

ENH: Removing special termination pipe from Windows implementation.  It does not need it because WaitForMultipleObjects can wait with a timeout for the process to terminate.  This is not the case in UNIX because waitpid has no timeout, so we need the termination pipe there.

ENH: Added special termination pipe to allow timeout to work for processes that close their output pipes.

ENH: Error messages from the forwarding executable are now read completely even if they are reported in multiple blocks.

BUG: When a child fails to exec, we need to read the entire error message, not just the first block.

BUG: Removed CloseHandle in case of error in DuplicateHandle.  According to documentation, DuplicateHandle will close the source handle regardless of error condition.

ENH: add the unix makefile generator as an option from the windows GUI, this builds with mingw, cygwin, and combinations of make cl, bcc32