fix align functions

[Freax13]

This pr fixes VirtAddr::align_up andVirtAddr::align_down. Previously those functions returned non-canonical addresses when aligning addresses near the address space gap. Two tests were added to test such cases.

This pr also fixesPhysAddr::align_up by adding a check to make sure the address is not too big.

[josephlr]

if we are panicking when the PhysAddr goes out of range, should we do the same if the VirtAddr goes out of range? It would make things more consistent.

[Freax13]

if we are panicking when the PhysAddr goes out of range, should we do the same if the VirtAddr goes out of range? It would make things more consistent.

This pr added just that:

x86_64/src/addr.rs

Lines 162 to 165 in 49b9204

	/// # Panics
	///
	/// This function panics if the resulting address is higher than
	/// `0xffff_ffff_ffff_ffff`.

[josephlr]

Thanks for adding the tests.