diagnostics: modernize the display of submessages

Since Bison 2.7, output was indented four spaces for explanatory
statements.  For example:

    input.y:2.7-13: error: %type redeclaration for exp
    input.y:1.7-11:     previous declaration

Since the introduction of caret-diagnostics, it became less clear.
Remove the indentation and display submessages as in GCC:

    input.y:2.7-13: error: %type redeclaration for exp
        2 | %type <float> exp
          |       ^~~~~~~
    input.y:1.7-11: note: previous declaration
        1 | %type <int> exp
          |       ^~~~~

* src/complain.h (SUB_INDENT): Remove.
(warnings): Add "note" to the enum.
* src/complain.h, src/complain.c (complain_indent): Replace by...
(subcomplain): this.
Adjust all dependencies.
* tests/actions.at, tests/diagnostics.at, tests/glr-regression.at,
* tests/input.at, tests/named-refs.at, tests/regression.at:
Adjust expectations.

1 files changed, 2 insertions, 9 deletions

diff --git a/src/scan-skel.l b/src/scan-skel.l
index 0cd308a8..2ffdcfc2 100644
--- a/src/scan-skel.l
+++ b/src/scan-skel.l
@@ -189,7 +189,7 @@ flag (const char *arg)
   else if (STREQ (arg, "fatal"))
     return fatal;
   else if (STREQ (arg, "note"))
-    return silent | complaint | no_caret;
+    return silent | complaint | no_caret | note;
   else if (STREQ (arg, "warn"))
     return Wother;
   else
@@ -225,14 +225,7 @@ at_complain (int argc, char *argv[], char **out_namep, int *out_linenop)
       boundary_set_from_string (&loc.end, argv[3]);
       locp = &loc;
     }
-  static int indent;
-  if (w & silent)
-    indent += SUB_INDENT;
-  else
-    indent = 0;
-  complain_args (locp, w, &indent, argc - 4, argv + 4);
-  if (w & silent)
-    indent -= SUB_INDENT;
+  complain_args (locp, w, argc - 4, argv + 4);
 }
 
 static void