Improved error reporting on invalid constant pool index

This will allow easy deduction of whether the invalid index comes from
some constant not being loaded (probably only slightly invalid) or
reading an irreveant byte when trying to read a constant pool index
(much larger than the constant pool size).

src/java_bytecode/java_bytecode_parser.cpp

@@ -79,6 +79,7 @@ class java_bytecode_parsert:public parsert
     if(index==0 || index>=constant_pool.size())
     {
       error() << "invalid constant pool index (" << index << ")" << eom;
+      error() << "constant pool size: " << constant_pool.size() << eom;
       throw 0;
     }