Give access to /proc/sys/vm/overcommit_memory to all domains

A lot of domain seems to be asking for the following rights:
allow * sysctl_vm_t:dir search;
allow * sysctl_vm_t:file { read open };

Digging a little, I found https://bugzilla.redhat.com/show_bug.cgi?id=872729 which lead me to:
- Fedora fix: https://git.fedorahosted.org/cgit/selinux-policy.git/commit/?id=343c0887514718387f36ee8ead2b941ba9bfb894
- Glibc change: https://sourceware.org/git/?p=glibc.git;a=commit;h=9fab36eb583c0e585e83a01253299afed9ea9a11

The access seems to be useless unless /proc/sys/vm/overcommit_memory contains '2', but I see no reasons not to allow it.

Compiling the policy works, but I can't use it right now as the genfscon proc does not seem to apply...