Re: [Libguestfs] [PATCH v4 11/24] nbd: Add types for extended headers

Add the constants and structs necessary for later patches to start implementing the NBD_OPT_EXTENDED_HEADERS extension in both the client and server, matching recent upstream nbd.git (through commit e6f3b94a934). This patch does not change any existing behavior, but merely sets the stage for upcoming patches. This patch does not change the status quo that neither the client nor server use a packed-struct representation for the request header. While most of the patch adds new types, there is also some churn for renaming the existing NBDExtent to NBDExtent32 to contrast it with NBDExtent64, which I thought was a nicer name than NBDExtentExt. Signed-off-by: Eric Blake<eblake(a)redhat.com>