Summary:
This diff changes the translation of global variables to translate the
initializer whenever it exists in LLVM, rather than relying on
linkage. Previously code such as
```
char *mutable_string = "hahaha";
```
would lead to LLVM code
```
nutritious_string = global i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str, i32 0, i32 0), align 8, !dbg !0 ; [#uses=2 type=i8**]
```
in which `mutable_string` had `External` linkage according to
`Llvm.linkage` even though it has an initializer. This could cause
sledge to drop the initializer.
Reviewed By: kren1
Differential Revision: D15577755
fbshipit-source-id: 50aa06c5e
Josh Berdine