factorize the bundling code then implement linux library bundling

factorize the bundling code then implement linux library bundling

• always rely on up-to-date x11 and gl libraries, bundling them will break on future distros
• gtk is not easily bundlable on linux because it looks for harcoded system path to optional shared libraries like image codecs, theme engines, sound notification system, etc. so expect user to install gtk first
• since we ask user to instal gtk, we can also ask them to install gtkglext, which is likely to pull gtk itself, x11 and gl dependencies
• old fontconfig does not work correctly if newer fontconfig configuration is installed
• if gtk and fontconfig is installed, freetype is