_virtualboxCreateMachine: Avoid unbounded stack
_virtualboxCreateMachine: Avoid unbounded stack

If the stars are in the right position and you're building with
VBox >= 4.2.0 it will happen that compiler thinks an array
allocated on the stack may be unbounded:

In file included from vbox/vbox_V4_2.c:13:0:
vbox/vbox_tmpl.c: In function '_virtualboxCreateMachine':
vbox/vbox_tmpl.c:2811:1: error: stack usage might be unbounded [-Werror=stack-usage=]
 _virtualboxCreateMachine(vboxGlobalData *data, virDomainDefPtr def, IMachine **machine, char *uuidstr ATTRIBUTE_UNUSED)
 ^

Well, given how the variable is declared, I had some hard time
seeing it is actually bounded. Surprisingly compiler does not
complain because of -Wframe-larger-than. This is because
variable length arrays do not count into that warning.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

VenkatDatta/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,nertpinx/libvirt,datto/libvirt,olafhering/libvirt,eskultety/libvirt,crobinso/libvirt,andreabolognani/libvirt,eskultety/libvirt,libvirt/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,zippy2/libvirt,crobinso/libvirt,datto/libvirt,taget/libvirt,fabianfreyer/libvirt,eskultety/libvirt,taget/libvirt,datto/libvirt,libvirt/libvirt,jfehlig/libvirt,libvirt/libvirt,olafhering/libvirt,andreabolognani/libvirt,jardasgit/libvirt,zippy2/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,taget/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,jardasgit/libvirt,zippy2/libvirt,andreabolognani/libvirt,crobinso/libvirt,datto/libvirt,nertpinx/libvirt,taget/libvirt,fabianfreyer/libvirt,taget/libvirt,crobinso/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,zippy2/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jardasgit/libvirt,datto/libvirt,eskultety/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,eskultety/libvirt,libvirt/libvirt,olafhering/libvirt