moved cwiid and all disis libs except disis_munger to externals/disis, and removed linux-specific build instructions from tar_em_up.sh

begin porting the disis_* dirs to a single library in externals/, starting with disis_phasor~.c.  We're just using the most recent version of pdlibbuilder to do the heavy lifting.

port agraef's commit from Pd-l2ork: Make 'tar_em_up.sh -B -n' do the right thing, by moving the extra staging done by 'make deb' into a separate 'debstage' target. commit 73bf25e1dd5bd2dd37e04e7e163855d440542e43

port aa6126adae5613d337cc71cee17b0078485dcc05 from Pd-l2ork: added temporary fix for rtcmix build until it is fixed upstream

add 105f71eba94f47ccdbf344f16a29758909a265e5 from Pd-l2ork: better pulling of submodules (TODO: add wiringpi as a submodule)

port 4a93e8e2ae2947d2322dde5d3233a68f82873774 from Pd-l2ork: minor improvements to the build script to accomodate new miXed submodule

port e885ea38fbe6f09d5ba38d5275444daf12077aa6 from Pd-l2ork: added redundant aclocal and autoconfig for the pd folder

updated tar_em_up.sh from pd-l2ork git. Note: this probably includes changes
from later commits

from pd-l2ork: 1e654625d71b6c0efae614cfa428e8cfae6e9b1e

from pd-l2ork: 640d3c53ad8cd592b1d757b988e27d3ada2b1779

*improved installer to make it easier to recompile pd-l2ork when continuing development after building a snapshot deb or tarball installer (the pd folder will retain config script with the appropriate --prefix flag)

*made disis_gpio and disis_spi buildable on all platforms (so that one can easily develop patches on a laptop and transport them onto RPi

improved installer to avoid install of Gem libraries when doing incremental install (should significantly shorten incremental installs)