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.

llvm-svn: 168197