Fix casts for mouse events on RenderWindow.

Use transmute instead of the 'as' keyword for c_uint -> int and c_float -> int
conversions. It might be useful to make those changes on other types of
windows.
Temporary fix of premature destruction of views.

Wrapped view obtained with get_*_view should not be automatically destroyed by
Drop. This is a temporary fix preventing the destruction of those views.
User-created views are still auto-destroyed by Drop.
Fix two more casts.
Merge pull request #1 from sebcrozet/master

Fix casts for mouse events on RenderWindow & premature view destruction.