ARM: follow up improvements for SVN r263118

The initial change was insufficiently complete for always getting the semantics
of __builtin_longjmp correct.  The builtin is translated into a
`tInt_eh_sjlj_longjmp` DAG node.  This node set R7 as clobbered.  However, the
code would then follow up with a clobber of R11.  I had failed to notice the
imp-def,kill on R7 in the isel.  Unfortunately, it seems that it is not possible
to conditionalise the Defs list via an !if.  Instead, construct a new parallel
WIN node and prefer that when targeting windows.  This ensures that we now both
correctly model the __builtin_longjmp as well as construct the frame in a more
ABI conformant manner.

llvm-svn: 263123