util: xml: Disallow aliasing of negative numbers in virXPathUInt
util: xml: Disallow aliasing of negative numbers in virXPathUInt

Passing negative number as an alias for the max value is an anti-feature
we unfortunately allowed in virsh, but luckily never encouraged in the
XML.

Refuse numbers with negative sign when parsing unsigned int from
XPaths.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

zippy2/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,libvirt/libvirt,libvirt/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,jfehlig/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,zippy2/libvirt