debug: feed single-line macro definitions and include hierachy to dfmt

At least DWARF can encode C-style macros. In doing so, it wants the
file include hierarchy, so give the debug format backend the option of
receiving that information from the preprocessor.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>

output/codeview.c

@@ -64,6 +64,8 @@ const struct dfmt df_cv8 = {
     cv8_init,                   /* .init */
     cv8_linenum,                /* .linenum */
     cv8_deflabel,               /* .debug_deflabel */
+    NULL,                       /* .debug_smacros */
+    NULL,                       /* .debug_include */
     NULL,                       /* .debug_mmacros */
     null_debug_directive,       /* .debug_directive */
     cv8_typevalue,              /* .debug_typevalue */