libical: upgrade 3.0.17 -> 3.0.18

libical: upgrade 3.0.17 -> 3.0.18

License-Update:
 LICENSE.LGPL21.txt - remove the KDAB claim for copyright

Changelog:
===========
-Requires CMake v3.5.0 or higher
-Escape ^ (U+005E) character in parameter values according to RFC 6868
-New CMake option LIBICAL_BUILD_EXAMPLES to disable building the examples
-Should be able to use the project as a submodule
-Built-in timezones updated to tzdata2024a

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>