Fix compilation of Enum on JDK 7

Change-Id: I2e58b6a527e4ef1fc7ed3359b8aea88d01a031fb
libcore: Better Enum fix for JDK 7

 * Jerome Pilliet suggests using a cast in the compareTo method instead of
   changing the field visibility. This is a much better fix.

Change-Id: I334105e0922225512a4d0a2d4b6c9c6ec71b9c51
Remove dead NioUtils.getDirectBufferAddress.

Change-Id: I764d86db1d74c5daf54cc925a9fc76db15a1107a
Fix BufferedReader.readLine to not read ahead after '\r'.

Bug: 8778372
Change-Id: I789d0ff5498cca48b16bb7b3b363014f7b6bcf95