Generalize addrmap dumping

While debugging another patch series, I wanted to dump an addrmap.  I
came up with this patch, which generalizes the addrmap-dumping code
from psymtab.c and moves it to addrmap.c.  psymtab.c is changed to use
the new code.

gdb/addrmap.c

@@ -590,6 +590,41 @@ addrmap_create_mutable (struct obstack *obstack)
   return (struct addrmap *) map;
 }
 
+/* See addrmap.h.  */
+
+void
+addrmap_dump (struct addrmap *map, struct ui_file *outfile, void *payload)
+{
+  /* True if the previously printed addrmap entry was for PAYLOAD.
+     If so, we want to print the next one as well (since the next
+     addrmap entry defines the end of the range).  */
+  bool previous_matched = false;
+
+  auto callback = [&] (CORE_ADDR start_addr, void *obj)
+  {
+    QUIT;
+
+    bool matches = payload == nullptr || payload == obj;
+    const char *addr_str = nullptr;
+    if (matches)
+      addr_str = host_address_to_string (obj);
+    else if (previous_matched)
+      addr_str = "<ends here>";
+
+    if (matches || previous_matched)
+      fprintf_filtered (outfile, "  %s%s %s\n",
+			payload != nullptr ? "  " : "",
+			core_addr_to_string (start_addr),
+			addr_str);
+
+    previous_matched = matches;
+
+    return 0;
+  };
+
+  addrmap_foreach (map, callback);
+}
+
 #if GDB_SELF_TEST
 namespace selftests {