Request for reviews (XL): 6978355: renaming for 6961697

[Christian Thalinger]

http://cr.openjdk.java.net/~twisti/6978355/webrev.01/

6978355: renaming for 6961697
Summary: This is the renaming part of 6961697 to keep the actual changes small for review.
Reviewed-by:

This is a split-off of 6961697 to make the review of the actual
changes easier.  This CR only does a couple of renames, moves code_*
methods into CodeBlob, adds a new CodeBuffer constructor to make code
simpler, adds some emit functions to CodeSection to make AD code
simpler, ...

I did the rename in two steps to make sure that no new
CodeBlob::code_* method is called instead of an old nmethod::code_*
method (which are now called nmethod::insts_*).