implement KVM_KVMCLOCK_CTRL. Interestingly, the kernel does not check 
the parameter. QEMU does pass 0 nevertheless as parameter.

bugzilla:  [Bug 339424] Full support of KVM ioctl


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14569 a5019735-40e9-0310-863c-91ae7b9d1cf9