sepcomp: add --semi-global to activate all semi-global optimizations
sepcomp: add --semi-global to activate all semi-global optimizations

Some numbers:

Note that `user` is the bootstrapped time, therefore we measure both the
compilation time and the execution time.
I suspect this is stupid from the point-of-view of any scientific methodology;
but, anyway, it is numbers and people like numbers.

~~~
$ nitg --separate nitg.nit
user	0m11.228s

$ nitg --separate --semi-global nitg.nit
user	0m9.736s

$ nitg --erasure nitg.nit
user	0m7.800s

$ nitg --erasure --rta nitg.nit
user	0m8.280s

$ nitg --erasure --rta --semi-global nitg.nit
user	0m7.648s
~~~

Signed-off-by: Jean Privat <51f8b1fa9b424745378826727452997ee2a7c3d7@pryen.org>

ablondin/nit,ventilooo/nit,jpcaissy/nit,MehdiAit/nit,ablondin/nit,jcbrinfo/nit,colinvidal/nit,jpcaissy/nit,colinvidal/nit,Freddrickk/nit,ppepos/nit,jcbrinfo/nit,itsWill/nit,ppepos/nit,itsWill/nit,colinvidal/nit,colinvidal/nit,privat/nit,ventilooo/nit,MehdiAit/nit,ablondin/nit,Freddrickk/nit,privat/nit,jcbrinfo/nit,Freddrickk/nit,ventilooo/nit,MehdiAit/nit,MehdiAit/nit,ventilooo/nit,MehdiAit/nit,itsWill/nit,privat/nit,jcbrinfo/nit,colinvidal/nit,jcbrinfo/nit,MehdiAit/nit,ventilooo/nit,privat/nit,MehdiAit/nit,colinvidal/nit,jcbrinfo/nit,itsWill/nit,ppepos/nit,ppepos/nit,colinvidal/nit,ppepos/nit,privat/nit,ventilooo/nit,privat/nit,Freddrickk/nit,itsWill/nit,itsWill/nit,ppepos/nit,Freddrickk/nit,jpcaissy/nit,jpcaissy/nit,ablondin/nit,ventilooo/nit,itsWill/nit,privat/nit,jpcaissy/nit,privat/nit,jpcaissy/nit,ablondin/nit,Freddrickk/nit,itsWill/nit,ablondin/nit,ventilooo/nit,jcbrinfo/nit,colinvidal/nit,ablondin/nit,Freddrickk/nit,MehdiAit/nit,Freddrickk/nit,jpcaissy/nit,MehdiAit/nit,privat/nit,privat/nit,jcbrinfo/nit,itsWill/nit,jpcaissy/nit,jcbrinfo/nit,ventilooo/nit,ppepos/nit,jcbrinfo/nit,ablondin/nit,itsWill/nit,ventilooo/nit,jcbrinfo/nit,MehdiAit/nit