vala: update 0.56.17 -> 0.56.18

vala: update 0.56.17 -> 0.56.18

- this update is required to work with gobject-introspection >= 1.83.2

Vala 0.56.18
============
 * Various improvements and bug fixes:
  - vala: Don't allow inheritance of compact class from non-compact class
  - vala, libvaladoc: Fix color support detection in log reporting
  - girparser: Handle `doc:format` element in root:repository [#1586]
  - codegen: Use correct ctype for result variable in methods in more cases
  - codegen: Fix conditional expression with only one void side
  - valadoc: Sync gir argument handling from valacompiler.vala
  - Update links to GNOME Wiki project and refer to new Vala websites
  - Add CI for tarball release service
 * Bindings:
  - gio-2.0: Improve the {Input,Output}Message bindings
  - glib-2.0: Fix the binding of `get_console_charset`
  - glib-2.0: Add missing CCode.array_null_terminated attributes to IConv.iconv()
  - glib-2.0: Make FileStream.*printf() return int [#1547]
  - glib-2.0: Update RegexMatchFlags and RegexCompileFlags's binding to 2.74
  - glib-2.0: Add Regex.escape_nul in GLib
  - gnu: add binding for 'relocate' APIs
  - gobject-2.0: Add TypeFlags missing values
  - gstreamer-1.0: Skip ParamSpecArray and ParamSpecFraction
  - libusb-1.0: Fix the LibUSB.TransferCb declaration
  - libusb-1.0: Fix the LibUSB.HotPlugCb declaration
  - sdl2: Fix CCode.destroy_function of SDL.RWops and usage of
    SDL.RWops.from_file() [#1550]
  - sdl2: Fix missing integer type for JoystickID [#1563]

Signed-off-by: Markus Volk <f_l_k@t-online.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>