Audit uses of apply_mark in built-in macros

Replace them with equivalents of `Span::{def_site,call_site}` from proc macro API.
The new API is much less error prone and doesn't rely on macros having default transparency.

src/libsyntax_ext/global_asm.rs

@@ -30,7 +30,7 @@ pub fn expand_global_asm<'cx>(cx: &'cx mut ExtCtxt<'_>,
                 id: ast::DUMMY_NODE_ID,
                 node: ast::ItemKind::GlobalAsm(P(global_asm)),
                 vis: respan(sp.shrink_to_lo(), ast::VisibilityKind::Inherited),
-                span: sp.with_ctxt(cx.backtrace()),
+                span: cx.with_legacy_ctxt(sp),
                 tokens: None,
             })])
         }