modtool: Fixed a bug in makexml for int-type io signatures
Merge remote-tracking branch 'martin/modtool/bugfix' into maint
Fix for #647 - GUI Tabs do not switch on WX GUI Scope sink channels on OSX

With this patch, the bug is not showing anymore. It was only tested by
me on Mac OS X - not on Linux nor other platforms.
The possible regressions introduced by fix should be limited to the
notebook chooser forms only.