Add missing dlls to Windows installer, add dynamic lib extensions for Windows and OSX to scripts/load_all_binaries.pd

* fix typo introduced into tar_em_up.sh
* remove flext and rtcmix from LIB_TARGETS
* selectively compile disis classes on Windows
* use Program Files (x86) for win64

remove dependence on libiberty for mingw in Makefile (not sure whether Cyrille will do this upstream)