gnulib: import mktime and move-if-change fixes from gnulib

gnulib: import mktime and move-if-change fixes from gnulib

* configure: Regenerate from the following.

2011-01-30  Paul Eggert  <eggert@cs.ucla.edu>

mktime: clarify long_int width checking
* lib/mktime.c (long_int_is_wide_enough): Move this assertion to
the top level, to make it clearer that the assumption about
long_int width is being checked.  See
<http://lists.gnu.org/archive/html/bug-gnulib/2011-01/msg00554.html>.

2011-01-29  Paul Eggert  <eggert@cs.ucla.edu>

TYPE_MAXIMUM: avoid theoretically undefined behavior
* lib/intprops.h (TYPE_MINIMUM, TYPE_MAXIMUM): Do not shift a
negative number, which the C Standard says has undefined behavior.
In practice this is not a problem, but might as well do it by the book.
Reported by Rich Felker and Eric Blake; see
<http://lists.gnu.org/archive/html/bug-gnulib/2011-01/msg00493.html>.
* m4/mktime.m4 (AC_FUNC_MKTIME): Likewise.
* lib/mktime.c (TYPE_MAXIMUM): Redo slightly to match the others.

mktime: #undef mktime before #defining it
* lib/mktime.c (mktime) [DEBUG]: #undef mktime before #defining it.

mktime: systematically normalize tm_isdst comparisons
* lib/mktime.c (isdst_differ): New function.
(__mktime_internal): Use it systematically for all isdst comparisons.
This completes the fix for libc BZ #6723, and removes the need for
normalizing tm_isdst.  See
<http://sourceware.org/bugzilla/show_bug.cgi?id=6723>
(not_equal_tm) [DEBUG]: Use isdst_differ here, too.

mktime: fix some integer overflow issues and sidestep the rest

This was prompted by a bug report by Benjamin Lindner for MinGW
<http://lists.gnu.org/archive/html/bug-gnulib/2011-01/msg00472.html>.
His bug is due to signed integer overflow (0 - INT_MIN), and I
I scanned through mktime.c looking for other integer overflow
problems, fixing all the bugs I found.

Although the C Standard says the resulting code is still not safe
in the presence of integer overflow, in practice it should be good
enough for all real-world two's-complement implementations, except
for debugging environments that deliberately trap on integer
overflow (e.g., gcc -ftrapv).

* lib/mktime.c (WRAPV): New macro.
(SHR): Also check that long_int and time_t shift right in the
usual way, before using the fast-but-unportable method.
(TYPE_ONES_COMPLEMENT, TYPE_SIGNED_MAGNITUDE): Remove, no longer
used.  The code already assumed two's complement, so there's
no need to test for alternatives.  All uses removed.
(TYPE_MAXIMUM): Don't rely here on overflow behavior not defined by
the C standard.  Problem reported by Rich Felker in
<http://lists.gnu.org/archive/html/bug-gnulib/2011-01/msg00488.html>.
(twos_complement_arithmetic): Also check long_int and time_t.
(time_t_avg, time_t_add_ok, time_t_int_add_ok): New functions.
(guess_time_tm, ranged_convert, __mktime_internal): Use them.
(__mktime_internal): Avoid integer overflow with unary subtraction
in two instances where -1 - X is an adequate replacement for -X,
since the calculations are approximate.

2011-01-29  Eric Blake  <eblake@redhat.com>

mktime: avoid infinite loop
* m4/mktime.m4 (AC_FUNC_MKTIME): Avoid overflow on possibly-signed
type; behavior is still undefined but portable to all known targets.
Reported by Rich Felker.

2011-01-28  Paul Eggert  <eggert@cs.ucla.edu>

mktime: avoid problems on NetBSD 5 / i386
* lib/mktime.c (long_int): New type.  This works around a problem
on NetBSD 5 / i386, where 'long int' and 'int' are both 32 bits
but time_t is 64 bits, and where I expect the existing code is
wrong in some cases.
(leapyear, ydhms_diff, guess_time_tm, __mktime_internal): Use it.
(ydhms_diff): Bring back the compile-time check for wide-enough
year and yday.

mktime: fix misspelling in comment
* lib/mktime.c (__mktime_internal): Fix misspelling in comment.
This merges all recent glibc changes of importance.

2011-01-28  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>

move-if-change: cope with concurrent mv of identical file.
* move-if-change (CMPPROG): Accept environment
variable as an override for `cmp'.
(usage): Document CMPPROG.
Adjust comparison to drop stdout.  Cope with failure of mv if
the target file exists and is identical to the source, for
parallel builds.
Report from H.J. Lu against binutils in PR binutils/12283.