All platforms already allow the omission of the call to Main and running
Windows on the main goroutine. This change just gets rid of Main, and
documents the special requirement on Window.Event.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
The app and app/internal/wm packages are tightly coupled, requiring
quite a bit of forwarding types, values and constants from the internal
package to export it. Further, no other package imports package wm.
This change merges the two packages.
While here, drop the pre-Go 1.14 SIGPIPE workaround.
Signed-off-by: Elias Naur <mail@eliasnaur.com>