V4 disasm: fix sub sp,sp,imm

This is a special-case instruction, where the immediate needs to be
multiplied by 4.

Change-Id: I86e5ab9d39d65b8eab99fae859969896c6e5630c
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
V4 JIT: fix stack size calculation on 32bit.

Registers containing outgoing parameters for calls are saved as Value
(so, 8 bytes long) instead of native register size. For 64 bit this is
the same, but not for 32 bits.

Change-Id: If1d55e9d552a301782816c9228390dc5611c6d00
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Touch up QJSEngine::evaluate documentation.

Change-Id: I350ad1ccb8a6cf522787e4579292fa4ba1c8e043
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>