Fix invalid LLVM IR for global.get/set of imported globals.

In passing, refactor global accesses and cache the address computations and values of const globals.

Also includes some cargo fmt fixes.

lib/compiler-llvm/src/compiler.rs

@@ -155,5 +155,4 @@ impl Compiler for LLVMCompiler {
         Ok(PrimaryMap::new())
         // unimplemented!("Dynamic funciton trampolines not yet implemented");
     }
-
 }