more explicit check of Java executable -- relevant for Linux x86/x86_64 mismatch and absence on Mac OS Lion;
more explicit check of Java executable -- relevant for Linux x86/x86_64 mismatch and absence on Mac OS Lion;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle