8146629: Make phase->is_IterGVN() accessible from Node::Identity and Node::Value
Summary: Change arguments of Node::Identity() and Node::Value() from PhaseTransform* to PhaseGVN*.
Reviewed-by: kvn, roland

8141132: JEP 254: Compact Strings
Summary: Adopt a more space-efficient internal representation for strings.
Reviewed-by: alanb, bdelsart, coleenp, iklam, jiangli, jrose, kevinw, naoto, pliden, roland, smarks, twisti
Contributed-by: Brent Christian <brent.christian@oracle.com>, Vivek Deshpande <vivek.r.deshpande@intel.com>, Tobias Hartmann <tobias.hartmann@oracle.com>, Charlie Hunt <charlie.hunt@oracle.com>, Vladimir Kozlov <vladimir.kozlov@oracle.com>, Roger Riggs <roger.riggs@oracle.com>, Xueming Shen <xueming.shen@oracle.com>, Aleksey Shipilev <aleksey.shipilev@oracle.com>, Sandhya Viswanathan <sandhya.viswanathan@intel.com>

8001532: C2 node files refactoring
Summary: Split C2 node files into cast, convert, countbits, intrinsic, move, narrowptr and opaquenode classes
Reviewed-by: kvn, morris