Sort includes according to style guidelines:

1. Main include corresponding to .cpp file, if any.
 2. DMD and LDC includes.
 3. LLVM includes.
 4. System includes.

Also updated a few include guards to match the default format.

driver/cl_options.cpp

@@ -9,7 +9,8 @@
 
 #include "driver/cl_options.h"
 #include "gen/cl_helpers.h"
-
+#include "gen/logger.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Target/TargetMachine.h"
 #if LDC_LLVM_VER >= 303
 #include "llvm/IR/DataLayout.h"
@@ -19,10 +20,6 @@
 #include "llvm/Target/TargetData.h"
 #endif
 
-#include "gen/logger.h"
-
-#include "llvm/Support/CommandLine.h"
-
 namespace opts {
 
 // Positional options first, in order: