gdb/breakpoint: use warning function instead of gdb_printf

Noticed that in breakpoint.c, in one place, we do this:

  gdb_printf (_("warning: Error removing "
                "breakpoint %d\n"),
                old_loc->owner->number);

Instead of using the `warning` function.  There are a number of
differences between using gdb_printf like this and calling `warning`,
the main one is probably that real warnings are sent to gdb_stderr,
while the above gdb_printf call will go to gdb_stdout.

In this commit I:

  1. Change to call `warning`, we can drop the "warning: " prefix from
  the string in breakpoint.c,

  2. Update the warning text, I now start with a lower case 'e', which
  I believe is the GDB style for warnings,

  3. And I have included the address of the bp_location in the warning
  messsage,

  4. Finally, I update all the tests (2) that include this error
  message.

Reviewed-By: Tom Tromey <tom@tromey.com>

gdb/breakpoint.c

@@ -11342,9 +11342,9 @@ update_global_location_list (enum ugll_insert_mode insert_mode)
 		     Note that at this point, old_loc->owner is still
 		     valid, as delete_breakpoint frees the breakpoint
 		     only after calling us.  */
-		  gdb_printf (_("warning: Error removing "
-				"breakpoint %d\n"), 
-			      old_loc->owner->number);
+		  warning (_("error removing breakpoint %d at %s"),
+			   old_loc->owner->number,
+			   paddress (old_loc->gdbarch, old_loc->address));
 		}
 	      removed = true;
 	    }

gdb/testsuite/gdb.base/break-main-file-remove-fail.exp

@@ -100,7 +100,7 @@ proc test_remove_bp { initial_load } {
 	# get_integer_valueof.
 	set munmap -1
 	gdb_test_multiple "print /d ${munmap_expr}" "get result of munmap call" {
-	    -re -wrap "^(?:warning: Error removing breakpoint $::decimal\r\n)?\\$\[0-9\]* = (\[-\]*\[0-9\]*).*" {
+	    -re -wrap "^(?:warning: error removing breakpoint $::decimal at $::hex\r\n)?\\$\[0-9\]* = (\[-\]*\[0-9\]*).*" {
 		set munmap $expect_out(1,string)
 		pass $gdb_test_name
 	    }
@@ -112,7 +112,7 @@ proc test_remove_bp { initial_load } {
 	}
 
 	gdb_test "delete \$bpnum" \
-	    "warning: Error removing breakpoint .*" \
+	    "^warning: error removing breakpoint $::decimal at $::hex" \
 	    "failure to remove breakpoint warns"
     }
 }

gdb/testsuite/gdb.base/hw-sw-break-same-address.exp

@@ -50,7 +50,7 @@ with_test_prefix "hw-sw" {
     # A bad GDB debugging against GDBserver would output a warning
     # here:
     #  delete breakpoints
-    #  warning: Error removing breakpoint 3
+    #  warning: error removing breakpoint 3 at <ADDRESS>
     #  (gdb) FAIL: gdb.base/hw-sw-break-same-address.exp: hw-sw: delete breakpoints
     gdb_test_no_output "delete breakpoints"
 }