i#1551 port to ARM: direct call mangling
i#1551 port to ARM: direct call mangling

Implements mangle_direct_call() for OP_bl.
Leaves OP_blx NYI as it is non-trivial due to the lack of OP_bx tha takes
an immediate.

Optimizes insert_mov_immed_ptrsz to avoid OP_movt if the top half of the
immediate is zero.

Review-URL: https://codereview.appspot.com/189410043

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