[Libvir] Request for changing #include directives to conform to Linux standard

[Philippe Berthault]

The 'virterror.h' file has an #include directive to "libvirt.h" which 
isn't correct
because libvirt include files are installed on a sub-directory named 
'libvirt'.
i.e. when libvirt is compiled with configure --script=/usr, then libvirt 
files are
installed in /usr/include/libvirt/.*

To be standard with Linux usage of include files, the correct directive in
virterror.h will be:
    #include <libvirt/libvirt.h>
instead of:
    #include "libvirt.h"

and in C/C++ source files using libvirt, there is just to include 
libvirt with:
    #include <libvirt/libvirt.h>
    #include <libvirt/virterror.h>

This is conform to Linux usage of include files and this permit to simplify
Makefile(s) because there is no need to add option -I/usr/include/libvirt
to compile sources files.

Regards.