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

debuild update: update to nw.js 0.15.4, remove DejaVu font from package for which we have a dependency anyway.

first shot at setting up the correct libs for Gem (have to put them in build/bin so that the dynamic loader finds them)

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 agraef's commit from Pd-l2ork: debuild: remove obsolete preinst and postrm scripts. commit a1424f03364e5cbb79a19ee4142c6b4c101f597c

port agraef's commit from Pd-l2ork: debuild: more permission fixes. commit 7a1dd816b0fcbb42f733e7e715d3323d15608d33