AnimationWML: fix issue with 'duration' and frame progressive images
Fix an include guard.

Issue spotted by Clang.
Restore original precision after writing a double

Found by coverity
Merge branch 'master' of github.com:wesnoth/wesnoth-old
[units.wesnoth.org] fix typo
Make the initially selected modificiation determine the button text
Assert that a pointer isn't null

Found by coverity
Merge branch 'master' of github.com:wesnoth/wesnoth-old