use IronTcl instead of tclkit

Because IronTcl scales text correctly while tclkit gets blurry text at
125% scaling in my testing.

May have something to do with SetProcessDpiAwareness, but I'm too tired
for that rabbit hole.

Makefile

@@ -17,7 +17,9 @@ linux:
 
 dist/GORTS-Windows.zip: windows
 	cd dist/windows; \
-		curl -L 'https://tclkits.rkeene.org/fossil/raw/tclkit-8.6.3-win32-x86_64.exe?name=403c507437d0b10035c7839f22f5bb806ec1f491' > tclkit.exe; \
+		curl -L 'https://www.irontcl.com/downloads/irontcl-amd64-8.6.7.zip' > irontcl.zip; \
+		unzip -o irontcl.zip; \
+		rm irontcl.zip; \
 		zip -r ../GORTS-Windows.zip .
 
 dist/GORTS-Linux.zip: linux

README.md

@@ -133,10 +133,10 @@ this program.  If not, see <https://www.gnu.org/licenses/>.
 Tcl options on Windows:
 
 - [TclKits](https://tclkits.rkeene.org/fossil/wiki/Downloads): single 5.8MiB
-  binary <== currently used
+  binary
 - [IronTcl](https://www.irontcl.com): 14.5Mib folder unzipped. Apparently
   IronTcl does text scaling perfectly out of the box (tested on Windows 10 with
-  125% scaling), while tclkit gets blurry.
+  125% scaling), while tclkit gets blurry. <== currently used
 - Manually compile? TODO
 
 Web server should probably read state from memory instead of disk (state.json).
@@ -191,5 +191,10 @@ The following is its original license:
 The default design uses `Jura` and `Noto Color Emoji` from Google Fonts. See
 their original licenses in `web/fonts/`.
 
+## Tcl/Tk
+
+GORTS bundles the [IronTcl][3] tcl/tk distribution.
+
 [1]: https://github.com/nhanb/orts
 [2]: https://www.libreoffice.org/discover/calc/
+[3]: https://www.irontcl.com/index.html

main_windows.go

@@ -9,7 +9,7 @@ import (
 	"github.com/lxn/win"
 )
 
-const DefaultTclPath = "./tclkit.exe"
+const DefaultTclPath = "./IronTcl/bin/wish86t.exe"
 
 func forceFocus(handle string) error {
 	hex := handle[2:] // trim the "0x" prefix