[update 3.0] #30121

30121
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10600 add environment: and class: compatibility methods to Compiler
        https://pharo.fogbugz.com/f/cases/10600
       
10598 MorphTreeNodeMorph draws wrongly drop highlight
        https://pharo.fogbugz.com/f/cases/10598
       
10599 AlainTreeModel not fully covered use of isCheckList
        https://pharo.fogbugz.com/f/cases/10599

Diff information:
http://smalltalkhub.com/mc/Pharo/Pharo30/main/Spec-Widgets-MarcusDenker.151.diff
http://smalltalkhub.com/mc/Pharo/Pharo30/main/Morphic-MarcusDenker.1429.diff
http://smalltalkhub.com/mc/Pharo/Pharo30/main/Compiler-MarcusDenker.454.diff