Fix issue 110 - enum declarations are treated as useless.
Enums are no longer considered forward-declarable.
Broke elaborated-type tests out of badinc into a dedicated test case.

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@487 812d1f90-f944-d88a-411a-122bdc93e1ea