New APIs: Implement stat calls that return nanosecond timestamps (RHBZ#1144891).

The existing APIs guestfs_stat, guestfs_lstat and guestfs_lstatlist
return a stat structure that contains atime, mtime and ctime fields
that store only the timestamp in seconds.

Modern filesystems can store timestamps down to nanosecond
granularity, and the ordinary glibc stat(2) wrapper will return these
in "hidden" stat fields:

  struct timespec st_atim;            /* Time of last access.  */
  struct timespec st_mtim;            /* Time of last modification.  */
  struct timespec st_ctim;            /* Time of last status change.  */

with the following macros defined for backwards compatibility:

  #define st_atime st_atim.tv_sec
  #define st_mtime st_mtim.tv_sec
  #define st_ctime st_ctim.tv_sec

It is not possible to redefine guestfs_stat to return a longer struct
guestfs_stat with room for the extra nanosecond fields, because that
would break the ABI of guestfs_lstatlist as it returns an array
containing consecutive stat structs (not pointers).  Changing the
return type of guestfs_stat would break API.  Changing the generator
to support symbol versioning is judged to be too intrusive.

Therefore this adds a new struct (guestfs_statns) and new APIs:

  guestfs_statns
  guestfs_lstatns
  guestfs_lstatnslist

which return the new struct (or array of structs in the last case).

The old APIs may of course still be used, forever, but are deprecated
and shouldn't be used in new programs.

Because virt tools are compiled with -DGUESTFS_WARN_DEPRECATED=1, I
have updated all the places calling the deprecated functions.  This
has revealed some areas for improvement: in particular virt-diff and
virt-ls could be changed to print the nanosecond fields.

FUSE now returns nanoseconds in stat calls where available, fixing
https://bugzilla.redhat.com/show_bug.cgi?id=1144891

Notes about the implementation:

- guestfs_internal_lstatlist has been removed and replaced by
  guestfs_internal_lstatnslist.  As the former was an internal API no
  one should have been calling it, or indeed can call it unless they
  start defining their own header files.

- guestfs_stat and guestfs_lstat have been changed into library-side
  functions.  They, along with guestfs_lstatlist, are now implemented
  as wrappers around the new functions which just throw away the
  nanosecond fields.

java/Makefile.inc

@@ -34,6 +34,7 @@ java_built_sources = \
 	com/redhat/et/libguestfs/PV.java \
 	com/redhat/et/libguestfs/Partition.java \
 	com/redhat/et/libguestfs/Stat.java \
+	com/redhat/et/libguestfs/StatNS.java \
 	com/redhat/et/libguestfs/StatVFS.java \
 	com/redhat/et/libguestfs/UTSName.java \
 	com/redhat/et/libguestfs/VG.java \

java/com/redhat/et/libguestfs/.gitignore

@@ -12,6 +12,7 @@ MDStat.java
 PV.java
 Partition.java
 Stat.java
+StatNS.java
 StatVFS.java
 UTSName.java
 VG.java