Fix crash when a network-request is aborted while forwarding data

Since we forward data block-wise a network request may be aborted while
we are still forwarding received data. In that case we should stop the
forwarding.

Task-number: QTBUG-41877
Change-Id: Ia34bbdcacdc4eb70a2e814d3b4bada9844abbb83
Reviewed-by: Michael Bruning <michael.bruning@digia.com>
Fix CLoop on big-endian machines

Callee and ScopeChain are JSObject pointers and saved in the 64bit
structure for JS registers. On a 32bit big-endian machine the actual
pointer is offset by the PayloadOffset of 4 bytes, but on little-endian
and 64bit architectures there is no offset.

This patch fixes four places the payloadOffset was not correctly added
on 32bit big-endian, and six places it was added on 64big big-endian
when it shouldn't.

Task-number: QTBUG-41896
Change-Id: I46b474bee9822b8040d1b7b2e8f31ce42e0adefe
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Do not use JIT on big endian architectures

All the JIT implementations targets the little-endian versions of ARM,
MIPS and SH4 respectively. So in case anyone builds on those platforms
we should not enable JIT.

Task-number: QTBUG-41896
Change-Id: I5be167511e2c3eac6c63e603b82da84fb6b29eaa
Reviewed-by: Julien Brianceau <jbriance@cisco.com>
Reviewed-by: Michael Bruning <michael.bruning@digia.com>