Small refactoring & reformatting in YETerm#compile
Prevent aliasing problem with UI shortcut methods

For UI terms we use shortcut methods, so e.g. instead of:

  term :HBox, ...

we emit:

  HBox(...)

This caused a problem when some unrelated |HBox| method was already in
scope. This commit fixes the problem by qualifying UI shortcut calls by
|UIShortcuts| in all such cases.