Preserve address space of forward-referenced global variables in the LL parser

Preserve address space of forward-referenced global variables in the LL parser

Before, the parser would assert on the following code:

@a2 = global i8 addrspace(1)* @a
@a = addrspace(1) global i8 0

because the type of @a was "i8*" instead of "i8 addrspace(1)*" when parsing
the initializer for @a2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168197 91177308-0d34-0410-b5e6-96231b3b80d8