ecj spams the console with irrelevant zip exceptions

[stephan-herrmann]

• improve error message
• remove printing of stack traces
• make err printout testable

Fixes #1578

[stephan-herrmann]

Implements the following idea from #1578:

@jukzi:
do not log stacktrace for ZipException - only log filename

@iloveeclipse:
I would be fine with that, assuming we produce error messages distinct enough to identify the exact place in compiler code that produces it.

I removed printStackTrace() only in one location, and at the same time improved the error messages as to tell the user, how exactly (by which command line option) the offending file entered compilation.

In order to make this testable, I also redirect the printout via Main.err (since plain System.err.println() almost never is a good idea to begin with).

This comes with the risk, that some build tools will only now begin to "see" these messages, and ecj cannot know, how those tools will interpret this (perhaps this will cause them to mark a compilation as failed).