7036706: G1: Use LIR_OprDesc::as_pointer_register in code changes for 7035117
Summary: Use LIR_OprDesc::as_pointer_register() instead as_register/as_register_lo combination in the code changes for 7035117.
Reviewed-by: iveresov
7036021: G1: build failure on win64 and linux with hs21 in jdk6 build environment
Summary: Missing parentheses around a casted expression and some missing casts were causing build failures with the jdk6 build tools.
Reviewed-by: kvn, brutisso