Fix address for cloning S2E via SSH.
Add info about terminating states to init_env howto.
Makefile uses system clang instead of custom clang.

This is required on my machine, because the downloaded clang 3.0 chokes
on the preinstalled GCC headers.

I also removed all address-sanitizer related Makefile targets. This
makes the Makefile smaller and compilation faster. Most people wouldn't
need the functionality anyway.
Fix indentation in init_env.c
Fix --select-process-code in init_env.c