Rewrite `StructLiteralExp::toElem` to store individual fields instead of generating a constant to fill the entire struct with a single `store`. This is much more efficient at compile time (fixing #320) and vastly reduces the size of the emitted code. Since LLVM no longer needs to keep the data for all fields in "registers" until the store happens, it should also be more efficient at run time in cases where the fields aren't assigned with constants. There's also some code clean-up by removing duplicated logic.

#ifndef LDC_GEN_OPTIMIZER_H
#define LDC_GEN_OPTIMIZER_H

namespace llvm { class Module; }

bool ldc_optimize_module(llvm::Module* m);

bool doInline();

int optLevel();

bool optimize();

#endif