fixed up dialog, backported some code from Pd-Vanilla 0.46

Move an ifdef with a GUI-messaging side-effect out of the way of an incrementally built gui message. (And possibly a good argument for why the gui_start_vmess interface might be a bad idea...)

fix some nasty regressions with drawnumber and drawsymbol due to Ivica and I overlooking fairly obvious compiler warnings :(

fix awful regression where deleting the end of a comment, a message, or the trailing arguments of an object didn't actually change the state of the object in Pd.

replacing literal "+" must come first

Cosmetic GUI changes: Reduce label font size in dialogs, enlarge prefs dialog window to fix bad line breaks in prefs dialog.

add my_canvas_class conditional in g_editor.c to disallow resize anchor, since it abuses an extra label handle for resizing.

This appears to be some complex bug with the @font-face rule in Chromium. The only surefire workaround I've found so far is to base64-encode the font and include it in a css file.

* check canvas visibility in iemgui_displace
* check visibility before updating scroll in canvas_dofont

quick fix for backslashes in legacy tcl commands breaking the GUI parser-- just send "dummy" command arg