Invoking, from within Basic, a method in a component of mine which throws a
WrappedTargetException, I found it somewhat unfortunate that the Basic IDE only
shows the message of the WrappedTargetException (which is of limited use to the
user, as it is often the case with "wrapping" exceptions), but not the message
of the exception which was actually wrapped.

Thus, I here propose a fix to the sbunoobj.cxx file, which actually unpacks a
"chain" of WrappedTargetExceptions. That is, if the
WrappedTargetException.TargetException member is a WrappedTargetException
itself, then it will also be handled, and so on.

For this, the patch modifies implHandleWrappedTargetException:
- first, if the exception is an InvocationTargetException, it is
  completely ignored. Note that this is what the old code does with
  completely ignoring any WrappedTargetException's message, silently
  assuming that it is always an InvocationTargetException.
- then, the message of the WrappedTargetException is appended to a string
  buffer.
- If the TargetException member of the error is also a WrappedTargetException,
  it continues with the previous step.
- If there is no WrappedTargetException anymore, but TargetException
  still contains an Exception object, this object's message is also
  appended.
- The special handling for BasicErrorException instances was preserved:
  "Traveling" the chain of WrappedTargetException's finishes if such
  a BasicErrorException is encountered.

Also, while I changed the code, I noticed there's a lot of duplicate code in the
exception handling, basically multiple
  catch ( FooException& e1 )
  {
    handleFooException( e1 );
  }
  catch( BarException& e2 )
  {
    handleBarException( e2 );
  }
  ...
blocks. Since there today exists a "::cppu::getCaughtException()", I took the
liberty to consolidate those blocks into single
  catch( const Exception& )
  {
    handleAnyException( ::cppu::getCaughtException() );
  }
blocks.

In the same course, the
  String implGetExceptionMsg( Exception& e )
was replaced with
  template< class EXCEPTION >
  String implGetExceptionMsg( const EXCEPTION& e )
, which means we now always display the type of the caught exception.