Incremental build of role files should avoid "incomplete build"

[stephan]

In some cases of incrementally compiling a role file the build will be incomplete signaled by ProblemReporter.notGeneratingCallinBinding().

This can be observed by incrementally compiling role file CalloutCompletionProposal where sibling role file StubUtility2 is wrongly read from the class file.

While this is correctly reported and a full build as advised actually solves the problem incremental build should actually take care of this situation.

[stephan]

Witness is in r18898, whereas the actual fix was already in r18897 (BuildManager?).

r18898 further helps the incremental builder to finish within fewer cycles, by marking the reported problem as Fatal|AbortType so that the next compile will actually grasp all required files.