asterisk: bump to 18.15.1

asterisk: bump to 18.15.1

This is a manual cherry-pick of commit
aa3bc352e787768fbf5f1f806a9b2b06a74b19fc as well as commit
b71770db4196e3eeefc01367e0d36a3f61d8ef85. The latter is currently in a
pull request to update asterisk to 18.15.1 in the openwrt-22.03 branch.

- add new modules
- res-geolocation depends on asterisk being built with libxlt support,
  but to make libxslt a general dependency is probably not a good idea
  for small devices, so this adds a config option
  ASTERISK_LIBXSLT_SUPPORT that is off by default except on x86_64
  builds
- refresh patches
- 180_build-fix-bininstall-launchd-issue-on-cross-platfrom.patch removed
  as included in upstream release
- added 170-menuselect-force-use-of-xml2-config.patch as upstream
  switched to use pkg-config for libxml2 detection, which would be fine,
  except OpenWrt's host libxml2 is static and Asterisk can't handle that
- the bump to 18.15.1 contains fixes for AST-2022-007, AST-2022-008 and
  AST-2022-009

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>