[hb-shape] Rename --show-messages to --trace

https://github.com/behdad/harfbuzz/issues/506

util/hb-shape.cc

@@ -76,7 +76,7 @@ struct output_buffer_t
       flags |= HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS;
     format_flags = (hb_buffer_serialize_flags_t) flags;
 
-    if (format.show_messages)
+    if (format.trace)
       hb_buffer_set_message_func (buffer, message_func, this, NULL);
   }
   void new_line (void)

util/options.cc

@@ -777,7 +777,7 @@ format_options_t::add_options (option_parser_t *parser)
     {"no-clusters",	0, G_OPTION_FLAG_REVERSE,
 			      G_OPTION_ARG_NONE,	&this->show_clusters,		"Do not output cluster indices",					NULL},
     {"show-extents",	0, 0, G_OPTION_ARG_NONE,	&this->show_extents,		"Output glyph extents",							NULL},
-    {"show-messages",	0, 0, G_OPTION_ARG_NONE,	&this->show_messages,		"Output shaping debug messages",					NULL},
+    {"trace",		0, 0, G_OPTION_ARG_NONE,	&this->trace,			"Output interim shaping results",					NULL},
     {NULL}
   };
   parser->add_group (entries,

util/options.hh

@@ -437,7 +437,7 @@ struct format_options_t : option_group_t
     show_unicode = false;
     show_line_num = false;
     show_extents = false;
-    show_messages = false;
+    trace = false;
 
     add_options (parser);
   }
@@ -479,7 +479,7 @@ struct format_options_t : option_group_t
   hb_bool_t show_unicode;
   hb_bool_t show_line_num;
   hb_bool_t show_extents;
-  hb_bool_t show_messages;
+  hb_bool_t trace;
 };
 
 /* fallback implementation for scalbn()/scalbnf() for pre-2013 MSVC */