revert back to case sensitive because you cant hold A and a at the same time

src/device/output/key/char_test.go

@@ -3,7 +3,6 @@ package key
 import "testing"
 
 func TestFromChar(t *testing.T) {
-	caseSensitive = false
 	if got := FromChar('1'); got != N1 {
 		t.Error(got)
 	}
@@ -22,11 +21,4 @@ func TestFromChar(t *testing.T) {
 	if got := ToChar(-1); got != '?' {
 		t.Error(got)
 	}
-	caseSensitive = true
-	if got := FromChar('a'); got != A {
-		t.Error(got)
-	}
-	if got := FromChar('A'); got != AUpper {
-		t.Error(got)
-	}
 }