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.

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

* 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

escape "\r" coming from Pd before evaluating

also some small formatting fixes

port b64e49c8af118dc953e56967b83cd5fe65f4ebd3 from Pd-l2ork: made cleaner and likely more universal implementation of the bendin fix

add 83fbd4f32f3d2b77b5967e4e6025c3b748a189ae to Pd-l2ork: fixed bendin incorrect value (was range of 0-16383, now is -8192 to 8191)

port 9f5a265fc83fe268b23dcc0393d69a018ed497c5 from Pd-l2ork: Fix broken sys_alsa_putmidibyte() in order to make midiout work on Linux

another kludge-- bring back the code in makefile.mingw to compile everything in extra, and remove the expr~ external files

add x_preset.c and x_magicglass.c back to makefile.mingw-- they were accidentally removed in the big Vanilla backport

very stupid kludge just to get the code to compile on Windows-- this needs to get fixed by a more complete backport of Pd Vanilla's s_path.c code