libroot: implement timegm calling the ICU backend

Change-Id: Ib4de4288e061670acbc2edea3671cee029305d33
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3748
Reviewed-by: Axel Dörfler <axeld@pinc-software.de>

Prepare for ICU update

- libicule and libiculx do not exist anymore in newer ICU versions
(harfbuzz replaces them), but we didn't actually use them, so remove
them from the build feature and from the package dependencies
- Add namespace usage marcos since the newer ICU packages put ICU things
in a namespace, making it easier to have multiple versions of ICU used
side by side.

No functional change intended, but this makes it possible to build the
code with either ICU 57 (for gcc2) or 66 (for other architectures).

Bring rewritten multibyte-support into repository.

* update copyrights of locale backend files

Multibyte-support has been rewritten to use ICU as backend.
While this does not necessarily work properly in every aspect
(e.g. the shell still has [different] problems with multibyte-
characters now), it does fix #6263 and #7700.

* fix support for influencing tzset() via TZ environment variable
(now at least <std> and <offset> are supported properly)
* instead of creating a TimeZone object whenever needed, we now
create it in tzset() and keep it around
* add tests for TZ to locale_test

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40788 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Merged weak-symbols branch.
* Fixed trivial merge conflict in src/system/libroot/posix/locale/nl_langinfo.cpp
* Fixed gcc 2 compilation of src/system/glue/init_term_dyn.c.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39571 a95241bf-73f2-0310-859d-f6bbb57e9c96

Adjust tzset() implementation to better follow the POSIX specs and
make some more perl tests happy.
* no longer expect a ICU timezone ID in the TZ environment variable,
but only expect this format if the TZ-value is starting with ':'
* accept "standard" TZ-values like "EST5" (of which only "EST" is
relevant to us) - if such a value is specified, we hardcode the
timezone name to the given value, no matter how ICU calls it
* adjust tests accordingly


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39415 a95241bf-73f2-0310-859d-f6bbb57e9c96

Optimised passing around of timezone a bit
* _kern_[sg]et_timezone() now accepts/passes out the timezone name, too
* adjust Time preflet and clockconfig to pass the timezone name into the kernel
when calling _kern_set_timezone()
* ajust implementation of tzset() to fetch the timezone name from the kernel
via _kern_get_timezone() instead of reading 'libroot_timezone_info'
* the Time preflet no longer writes 'libroot_timezone_info'


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38164 a95241bf-73f2-0310-859d-f6bbb57e9c96

Implement tzset(), gmtime(), localtime() and mktime() on top of ICU
* no longer keep a separate time-backend, since the implementation needs to
access (data of) the locale backend anyway
* moved more stuff from localtime_fading_out.c to localtime.cpp
* added respective tests to locale_test
* added two more tests copied from glibc, test_time.c and tst-mktime.c


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38162 a95241bf-73f2-0310-859d-f6bbb57e9c96

Bring rewritten multibyte-support into repository.

* update copyrights of locale backend files

Multibyte-support has been rewritten to use ICU as backend.
While this does not necessarily work properly in every aspect
(e.g. the shell still has [different] problems with multibyte-
characters now), it does fix #6263 and #7700.

* fix support for influencing tzset() via TZ environment variable
(now at least <std> and <offset> are supported properly)
* instead of creating a TimeZone object whenever needed, we now
create it in tzset() and keep it around
* add tests for TZ to locale_test

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40788 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Merged weak-symbols branch.
* Fixed trivial merge conflict in src/system/libroot/posix/locale/nl_langinfo.cpp
* Fixed gcc 2 compilation of src/system/glue/init_term_dyn.c.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39571 a95241bf-73f2-0310-859d-f6bbb57e9c96

Adjust tzset() implementation to better follow the POSIX specs and
make some more perl tests happy.
* no longer expect a ICU timezone ID in the TZ environment variable,
but only expect this format if the TZ-value is starting with ':'
* accept "standard" TZ-values like "EST5" (of which only "EST" is
relevant to us) - if such a value is specified, we hardcode the
timezone name to the given value, no matter how ICU calls it
* adjust tests accordingly


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39415 a95241bf-73f2-0310-859d-f6bbb57e9c96

Optimised passing around of timezone a bit
* _kern_[sg]et_timezone() now accepts/passes out the timezone name, too
* adjust Time preflet and clockconfig to pass the timezone name into the kernel
when calling _kern_set_timezone()
* ajust implementation of tzset() to fetch the timezone name from the kernel
via _kern_get_timezone() instead of reading 'libroot_timezone_info'
* the Time preflet no longer writes 'libroot_timezone_info'


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38164 a95241bf-73f2-0310-859d-f6bbb57e9c96

Implement tzset(), gmtime(), localtime() and mktime() on top of ICU
* no longer keep a separate time-backend, since the implementation needs to
access (data of) the locale backend anyway
* moved more stuff from localtime_fading_out.c to localtime.cpp
* added respective tests to locale_test
* added two more tests copied from glibc, test_time.c and tst-mktime.c


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38162 a95241bf-73f2-0310-859d-f6bbb57e9c96