dune

[libdune] initial support for FPU state management

[kern] Cleanups to ept.c and fix a bug where memory could leak when a large page mapping replaces a region mapped with small pages.

[kern] Remove comment about vmcs_clear(). We call vmcs_clear() in the vmx_destroy_vcpu() path, so by the time the module is removed (with refcount 0) all loaded VMCS's will have been cleared.

[kern] add Dune support for INVPCID, a new TLB management instruction becoming available in Haswell

Fix an issue where reference counts to the dune char device and module would be left lingering when a Dune process exits. As a result, there are no longer situations where it is impossible to unload the Dune module.