* Makefile.in: Add 'cygwin' subdirectory to 'make all'

	* Makefile.in: Add 'cygwin' subdirectory to 'make all'
	target.
	* configure.in: Configure 'cygwin' and 'win' directory
	for a cygwin host.
	* configure: Regenerated.
	* cygwin/configure.in: Change version number to 8.3.
	* cygwin/configure: Regenerated.
	* cygwin/Makefile.am: Added/removed files to be build
	for Tcl8.3.
	* cygwin/Makefile.in: Regenerated.
	* generic/tcl.h: Don't define __WIN32__ for cygwin or
	mwing32 builds.  Don't define USE_TCLALLOC when building
	for cygwin.  Don't use __declspec unless building Tcl or
	tk or build with USE_TCL_STUBS.
	* generic/tclAlloc.c: For cygwin hosts, don't using
	anything in this file unless build with __TCL_UNIX_VARIANT.
	* generic/tclClock.c: Declare 'timezone' as an int, if it
	hasn't been #defined.
	* generic/tclStubInit.c: Don't export any tclAlloc function
	when build for a cygwin host.
	* win/configure.in: Set DL_LIBS and MATH_LIBS.  Create
	unix/tclConfig.sh.
	* win/configure: Regenerated.
	* win/tclWinPort.h: Added missing #endif.
	* win/tclWinFile.c (TclpChdir): Don't invert change
	directory results on cygwin.