Prevent Tux from climbing while swimming (#3017)

Climbable did not check if Tux is swimming and thus affects Tux's velocity. A check for is_swimming() is added to prevent this.

Fixes #2981

src/trigger/climbable.cpp

@@ -122,7 +122,7 @@ void
 Climbable::event(Player& player, EventType type)
 {
   if (type == EVENT_ACTIVATE || (type == EVENT_TOUCH && player.get_controller().hold(Control::UP))) {
-    if (player.get_grabbed_object() == nullptr){
+    if (player.get_grabbed_object() == nullptr && !player.is_swimming()){
       auto it = std::find_if(trying_to_climb.begin(), trying_to_climb.end(),
         [&player](const ClimbPlayer& element)
         {
@@ -161,6 +161,7 @@ Climbable::event(Player& player, EventType type)
 bool
 Climbable::may_climb(const Player& player) const
 {
+  if (player.is_swimming()) return false;
   if (player.get_bbox().get_left() < m_col.m_bbox.get_left() - GRACE_DX) return false;
   if (player.get_bbox().get_right() > m_col.m_bbox.get_right() + GRACE_DX) return false;
   if (player.get_bbox().get_top() < m_col.m_bbox.get_top() - GRACE_DY) return false;