repo cleanup: remove tcl/tk build infrastructure and scripts, old patches, automated build scripts for pd-extended, old gui plugins, and unnecessary install-time dependencies

port bccbccc9bb53cdc7f2e5238345f69fd754507595 from Pd-l2ork: finally fixed control file for both pre and post 15.10 Ubuntu due to libgsl

port b39417b3d4676fb3275aa31be934fe776718504c from Pd-l2ork: experimental improvements to the Linux build to make it compatible with Ubuntu 16.04

*updated dependencies that reflect rtcmix~ external needs

from pd-l2ork: a7f382e3d4ffd84c0e7246fdc2d24afca81784f9

hopefully improved libglew support due to unfortunately named libs that limit their flexible rollout across different versions of Ubuntu (and likely other distros as well)