test/CodeGenCXX/dllexport.cpp: don't instantiate templates in USEMEMFUNC macro

Use the derived class in the macro instead, to make it unambigous where
the template is being instantiated.
[ARM] Mark VSETLNi32 with the InsertSubreg property and implement the related
target hook.

This patch teaches the compiler that:
dX = VSETLNi32 dY, rZ, imm
is the same as:
dX = INSERT_SUBREG dY, rZ, translateImmToSubIdx(imm)

<rdar://problem/12702965>