rollup merge of rust-lang#24762: nrc/mod-debug-2

Closes rust-lang#20780

r? @michaelwoerister

I'm sure this could be done better with deeper knowledge of debuginfo, but this seems like a good start.

Author: alexcrichton

src/librustc_trans/trans/base.rs

@@ -2182,7 +2182,7 @@ pub fn create_entry_wrapper(ccx: &CrateContext,
         unsafe {
             llvm::LLVMPositionBuilderAtEnd(bld, llbb);
 
-            debuginfo::insert_reference_to_gdb_debug_scripts_section_global(ccx);
+            debuginfo::gdb::insert_reference_to_gdb_debug_scripts_section_global(ccx);
 
             let (start_fn, args) = if use_start_lang_item {
                 let start_def_id = match ccx.tcx().lang_items.require(StartFnLangItem) {