Request for reviews (M): 7009756: volatile variables could be broken throw reflection API

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/7009756/webrev

Fixed 7009756: volatile variables could be broken throw reflection API

Unsafe_SetLongVolatile() and Unsafe_GetLongVolatile() are not atomic
on 32 bit x86 (C++ generates two 32 bit loads/stores).

Use Atomic::load() and Atomic::store() to access a volatile long.

Verified with bug's test on all 32 bit platforms. Passed JPRT.