Improve usability and/or readibility of help and apropos output.

The "help" command can output long list of command names or classes.
Use the title style to style the command names or classes to make
the output more readable.

Similarly, change "apropos" command to also style the command names.

It is sometimes unclear why "apropos REGEXP" lists some commands,
and then the user has to manually do 'help command' for all commands
listed by "apropos" to see more details about the matching commands.

=> Add an optional flag -v so that "apropos -v REGEXP":
  * outputs the full documentation of matching commands.
  * highlights the documentation parts matching REGEXP.

gdb/cli/cli-decode.c

@@ -23,6 +23,7 @@
 #include "ui-out.h"
 #include "cli/cli-cmds.h"
 #include "cli/cli-decode.h"
+#include "cli/cli-style.h"
 #include "common/gdb_optional.h"
 
 /* Prototypes for local functions.  */
@@ -937,14 +938,42 @@ add_com_suppress_notification (const char *name, enum command_class theclass,
 					&cmdlist, suppress_notification);
 }
 
+/* If VERBOSE, print the full help for command C and highlight the
+   documentation parts matching HIGHLIGHT,
+   otherwise print only one-line help for command C.  */
+
+static void
+print_doc_of_command (struct cmd_list_element *c, const char *prefix,
+		      bool verbose, compiled_regex &highlight,
+		      struct ui_file *stream)
+{
+  /* When printing the full documentation, add a line to separate
+     this documentation from the previous command help, in the likely
+     case that apropos finds several commands.  */
+  if (verbose)
+    fputs_filtered ("\n", stream);
+
+  fprintf_styled (stream, title_style.style (),
+		  "%s%s", prefix, c->name);
+  fputs_filtered (" -- ", stream);
+  if (verbose)
+    fputs_highlighted (c->doc, highlight, stream);
+  else
+    print_doc_line (stream, c->doc);
+  fputs_filtered ("\n", stream);
+}
+
 /* Recursively walk the commandlist structures, and print out the
    documentation of commands that match our regex in either their
    name, or their documentation.
+   If VERBOSE, prints the complete documentation and highlight the
+   documentation parts matching REGEX, otherwise prints only
+   the first line.
 */
-void 
-apropos_cmd (struct ui_file *stream, 
+void
+apropos_cmd (struct ui_file *stream,
 	     struct cmd_list_element *commandlist,
-	     compiled_regex &regex, const char *prefix)
+	     bool verbose, compiled_regex &regex, const char *prefix)
 {
   struct cmd_list_element *c;
   int returnvalue;
@@ -960,10 +989,7 @@ apropos_cmd (struct ui_file *stream,
 	  /* Try to match against the name.  */
 	  returnvalue = regex.search (c->name, name_len, 0, name_len, NULL);
 	  if (returnvalue >= 0)
-	    {
-	      print_help_for_command (c, prefix, 
-				      0 /* don't recurse */, stream);
-	    }
+	    print_doc_of_command (c, prefix, verbose, regex, stream);
 	}
       if (c->doc != NULL && returnvalue < 0)
 	{
@@ -971,10 +997,7 @@ apropos_cmd (struct ui_file *stream,
 
 	  /* Try to match against documentation.  */
 	  if (regex.search (c->doc, doc_len, 0, doc_len, NULL) >= 0)
-	    {
-	      print_help_for_command (c, prefix, 
-				      0 /* don't recurse */, stream);
-	    }
+	    print_doc_of_command (c, prefix, verbose, regex, stream);
 	}
       /* Check if this command has subcommands and is not an
 	 abbreviation.  We skip listing subcommands of abbreviations
@@ -983,7 +1006,7 @@ apropos_cmd (struct ui_file *stream,
 	{
 	  /* Recursively call ourselves on the subcommand list,
 	     passing the right prefix in.  */
-	  apropos_cmd (stream,*c->prefixlist,regex,c->prefixname);
+	  apropos_cmd (stream, *c->prefixlist, verbose, regex, c->prefixname);
 	}
     }
 }
@@ -1126,6 +1149,9 @@ Type \"help all\" for the list of all commands.");
   fputs_filtered ("documentation.\n", stream);
   fputs_filtered ("Type \"apropos word\" to search "
 		  "for commands related to \"word\".\n", stream);
+  fputs_filtered ("Type \"apropos -v word\" for full documentation", stream);
+  wrap_here ("");
+  fputs_filtered (" of commands related to \"word\".\n", stream);
   fputs_filtered ("Command name abbreviations are allowed if unambiguous.\n",
 		  stream);
 }
@@ -1212,10 +1238,12 @@ static void
 print_help_for_command (struct cmd_list_element *c, const char *prefix,
 			int recurse, struct ui_file *stream)
 {
-  fprintf_filtered (stream, "%s%s -- ", prefix, c->name);
+  fprintf_styled (stream, title_style.style (),
+		  "%s%s", prefix, c->name);
+  fputs_filtered (" -- ", stream);
   print_doc_line (stream, c->doc);
   fputs_filtered ("\n", stream);
-  
+
   if (recurse
       && c->prefixlist != 0
       && c->abbrev_flag == 0)