build failure after libcmis update

Hi,

some of you may have experienced the same problem as I--build of recent
master breaks in ucb/src/ucp/cmis with something like:

error: ‘AllowableActionsPtr’ does not name a type

It turns out this is caused by stale libcmis headers in solver, because
the unpacked header has modification time 2012-Aug-09 12:27 , which is
way older than the current copy in solver. The old build system
workarounded that by copying the delivered headers to $(OUT)/inc first
(by listing them in OUT2INC variable). That seems unnecessary to me;
instead, I propose to add --touch to tar options, so the files are
extracted with modification times set to extraction time. According to
tar's changelog, this option exists since 1995, so it should be
supported on all our platforms :-) Any objections?

Note: This might be a bit harder to achieve for unzip: the equivalent
option is -D, but I am not sure it is supported everywhere. In
particular, I know that -DD (which extends the modification time change
to directories as well) does not work on MacOS X, because I had used it
in solenv/gbuild/UnpackedTarball.mk orginally and had to throw it out,
because the MacOS tinderbox(es) were unhappy about it. Could someone try
if plain -D works?

D.