Updates to install-all.sh

Use main apt-get git repo
Use main libstrophe git repo
Configure libstrophe with --prefix==/usr on cygwin
Use 0.8.6 tag of libstrophe
Added libtool to dependencies in install-all.sh
Added --prefix=/usr to all libstrophe installs
Removed AC_FUNC_MALLOC
Make prefix and argument to libstrophe install