i#1551 port to ARM: add Thumb support to fcache_{enter,return}
i#1551 port to ARM: add Thumb support to fcache_{enter,return}

We can't push or pop sp in Thumb mode.

Review-URL: https://codereview.appspot.com/196290043

daksunt/dynamorio,bl4ckic3/dynamorio,sigma-random/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,sigma-random/dynamorio,bl4ckic3/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,code4bones/dynamorio,code4bones/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,daksunt/dynamorio