api: add overflow error

Overflow can be user-induced, so it deserves more than being called
an internal error.  Note that in general, 32-bit platforms have
far more places to trigger this error (anywhere the public API
used 'unsigned long' but the other side of the connection is a
64-bit server); but some are possible on 64-bit platforms (where
the public API computes the product of two numbers).

* include/libvirt/virterror.h (VIR_ERR_OVERFLOW): New error.
* src/util/virterror.c (virErrorMsg): Translate it.
* src/libvirt.c (virDomainSetVcpusFlags, virDomainGetVcpuPinInfo)
(virDomainGetVcpus, virDomainGetCPUStats): Use it.
* daemon/remote.c (HYPER_TO_TYPE): Likewise.
* src/qemu/qemu_driver.c (qemuDomainBlockResize): Likewise.

include/libvirt/virterror.h

@@ -4,7 +4,7 @@
  * Description: Provides the interfaces of the libvirt library to handle
  *              errors raised while using the library.
  *
- * Copy:  Copyright (C) 2006, 2010-2011 Red Hat, Inc.
+ * Copy:  Copyright (C) 2006, 2010-2012 Red Hat, Inc.
  *
  * See COPYING.LIB for the License of this software
  *
@@ -246,6 +246,7 @@ typedef enum {
     VIR_ERR_AUTH_CANCELLED = 79,        /* authentication cancelled */
     VIR_ERR_NO_DOMAIN_METADATA = 80,    /* The metadata is not present */
     VIR_ERR_MIGRATE_UNSAFE = 81,        /* Migration is not safe */
+    VIR_ERR_OVERFLOW = 82,              /* integer overflow */
 } virErrorNumber;
 
 /**