update x11-wm/fvwm2 to conflict with this new port on install.
While here, remove a patch that had no effect.
The patch in question did a 'cd' in a make recipe, which won't work, every line of a recipe is executed by its own shell. The resulting package is the same without the patch.
The patching for M4 is gone because fvwm3 doesn't include the module any more.
Things missing: GO support. This new port disables GO for now, because fetching using the go:modules facility doesn't work, I might look for help with it upstream later. So far, it doesn't matter much, the new GO module FvwmPrompt is just a replacement for FvwmCommand and FvwmConsole, which are still available.