Request for reviews (S): 6932536: JSR 292 modified JDK MethodHandlesTest fails on x86_64

[Christian Thalinger]

http://cr.openjdk.java.net/~twisti/6932536/webrev.01/

Changing the nextArg value of MethodHandlesTest to be bigger than
Integer.MAX_VALUE to actually test long arguments reveals a bug on
x86_64.

There were actually two bugs:

1. For i2l and unboxi long values were stored in two slots as 32-bit
words instead of a 64-bit one.

2. The stack-move conversion value was read as 32-bit value and then
shifted which resulted in e.g. 0xffffffff values in 64-bit registers
instead of -1.

Tested: MethodHandlesTest