Fix --select-process-code in init_env.c

(always select module init_env.so)
Reformatted help message

Reported-by: Jonas Wagner <jonas.wagner@epfl.ch>
Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>
init_env: disable custom instruction for debug build

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>
S2EExecutor: warning should be printed when at least 2 states, not 1

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>