Correct issues with the test support for jdk.test.lib.hexdump.HexPrinter.
 - Correct the swapped definitions of ASCII and PRINTABLE
   Printable should always return a single character,
   ASCII provides mnemonics to be consistent with the command line hexdump.

 - For the methods to format ByteBuffers align the descriptions of the index and length to match ByteBuffer.

 - Correctly implement the extraction of bytes from the ByteBuffer

 - a newline in the annotation should print as '\n' instead of causing a line break