Request for review(S) 6955349: C1: Make G1 barriers work with x64

[Igor Veresov]

This fixes G1 barriers in c1 on x64.

I've also changed the type of disp (was int now intx) in LIR_Address 
constructor in order to make recent invokedynamic changes compile on 64 
bit and to make it consistent with c2.

Webrev: http://cr.openjdk.java.net/~iveresov/6955349/webrev.00/

Thanks!
igor