Rename global window vars to sane names

Global vars "width", "height", "baseline",
and "maximized" are now prefixed with
"utox_window_".

They, especially width and height, were shadowed
too often, not to mention that short simple names
for global vars is simply not healthy.
Add -Wshadow to Makefile
Fix shadowing of redraw() in edit.c
Fix shadowing of len in messages_draw()
Fix shadowing of x in messages_draw()
Fix shadowing of redraw() in messages_mmove()
Fix shadowing of data in messages_selection()
Fix shadowing of self in log_write()
Fix shadowing of size in load_save()
Fix shadowing of msg in tox_message()
Fix shadowing of p in tox_transfer.c
Fix shadowing of dx/dy in ui.c
Fix shadowing of r in tox_av.h
Fix shadowing of fd global variable in xlib/*
Fix shadowing of event in xlib/event.c
Fix shadowing of font in font_open()
Fix shadowing of i in freefonts()
Fix shadowing of i in get_color_profile()
Merge branch 'add-wshadow' of https://github.com/albel727/uTox

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