Use the correct address space when emitting the ctor function list

Use the correct address space when emitting the ctor function list

This patch modifies clang so that, if compiling for a target that
explicitly specifies a nonzero program memory address space, the
constructor list global will have the same address space as the
functions it contains.

AVR is the only in-tree backend which has a nonzero program memory
address space.

Without this, the IR verifier would always fail if a constructor
was used on a Harvard architecture backend.

This has no functional change to any in-tree backends except AVR.

llvm-svn: 346520