DirectoryIndexer: Handle SecurityException

Hi there,

@dscho, thanks for the help again! I will test it on Windows these days. On Linux it works, with your example. Anyway: If I want to use the builder in my Eclipse-OSGi Plugin I get the following exception:

Exception in thread "main" java.lang.SecurityException: class "org.eclipse.swt.browser.BrowserInitializer"'s signer information does not match signer information of other classes in the same package

I think this exception occurs, as we try to load another eclipse plugin outside the eclipse enviroment (plugins are signed, but not the classes). If I catch the SecurityException (which is thrown in line 91 in the DirectoryIndexer), and simply skip the classes, it works just fine.

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This commit skips classes which can't be loaded due to a SecurityException during
the annotation pre-processing using the Eclipse Helper. Reason: Not all
classes of a eclipse-plugin can't be loaded outside the eclipse-enviroment,
i.e. from a "normal" java program. If you try to load them during
annoation-preprocessing using the EclipseHelper, the SecurityException
is thrown.