Most APIs use 'unsigned int flags'; but a few stragglers were using
a signed value.  In particular, the vir*GetXMLDesc APIs were
split-brain, with inconsistent choice of types.  Although it is
an API break to use 'int' instead of 'unsigned int', it is ABI
compatible (pre-compiled apps will have no difference in behavior),
and generally apps can be recompiled without any issue (only rare
apps that compiled with extremely high warning levels, or which
pass libvirt API around as typed function pointers, would have to
make any code changes to deal with the change).

The migrate APIs use 'unsigned long flags', which can't be changed,
due to ABI constraints.

This patch intentionally touches only the public API, to prove the
claim that most existing code (including driver callbacks and virsh)
still compiles just fine in spite of the type change.

* include/libvirt/libvirt.h.in (virConnectOpenAuth)
(virDomainCoreDump, virDomainGetXMLDesc, virNetworkGetXMLDesc)
(virNWFilterGetXMLDesc): Use unsigned int for flags.
(virDomainHasCurrentSnapshot): Use consistent spelling.
* src/libvirt.c (virConnectOpenAuth, virDomainCoreDump)
(virDomainGetXMLDesc, virNetworkGetXMLDesc)
(virNWFilterGetXMLDesc, do_open): Update accordingly.