Bytecode-level API.

This package provides low-level API for editing a raw class file. It allows the users to read and modify a constant pool entry, a single bytecode instruction, and so on.

The users of this package must know the specifications of class file and Java bytecode. For more details, read this book:

- Tim Lindholm and Frank Yellin, "The Java Virtual Machine Specification 2nd Ed.", Addison-Wesley, 1999.