[SYSREG2] makefile: improve revision.c and virt.cpp

[SergeGautherie]

• makefile: Move 'rm revision.c' to 'clean' target
  And add '/revision.c' to '.gitignore'.

This makes it easy to check revision.c content.
And seems more consistent to me.

--

• Rename 'virt.cpp' to 'sysreg2.cpp'

Let us be explicit and not confuse with 'libvirt.cpp'.

[HeisSpiter]

I don't see the point of this pull request and this changes.
Can you explain before I close? What are you trying to achieve?

[SergeGautherie]

Can you explain before I close? What are you trying to achieve?

I am not sure what I could add to what I already wrote...

These are two points I noticed when I started to look at this code:

• current filename makes it unobvious at first glance where main() is,
• current makefile makes it complicated to work on issues like [SYSREG2] Upgrade "revision.c" to Git from SVN #1.

[HeisSpiter]

Closing, given it provides no clear improvement.