[SRU] Update to vala 0.40.19 in bionic

The 0.40.x series is maintained as LTS release and will receive further bug fix releases in the future. See https://wiki.gnome.org/Projects/Vala

Previous 0.40.17 SRU https://bugs.launchpad.net/bugs/1803136

Falls under the standing GNOME SRU execption
https://wiki.ubuntu.com/StableReleaseUpdates#GNOME

Upstream changes since 0.40.17:

Vala 0.40.19
============
 * Various improvements and bug fixes:
   - codegen:
    + Fix precondition in creation method of structs
    + Don't set implemenation of interface property to its own [#891]
    + Use result value of assignment rather than its computation [#895]
    + Cast instance parameter in member-initializer for base-properties [#899]
    + Skip StructRegisterFunction for boolean/integer/floating types [#901]
    + Handle different type-symbols in visit_base_access() [#901]
   - vala:
    + VoidType is actually compatible with itself [#878]
    + Keep formal_target_type on transform of method-call/object-creation [#835]
    + Add a basic parameter check for [Print] methods
    + Don't ignore inner errors in Block and acknowledge them further
    + Don't report further errors if MemberInitializer.check() failed
    + Improve error message for unsupported inner types and declarations
    + Don't allow "va_list" as return-type or type of fields [#884]
    + Check before accessing "name" of parent_symbol which might be null
    + Allow to override base interface properties explicitly
    + Fix base-access check for compact classes
    + Improve detection of recursive struct declarations [#902]
    + Inline allocated arrays require length or initializer [#903]
    + Don't ignore errors in Parameter and acknowledge them further
  - parser: Implicit "main" method of main-block is public and static
  - genie: Fix parser's inner state when a struct is declared after a class
  - girparser: Apply explicitly given ctype metadata attributes on callables
  - testrunner: Invalid tests and therefore expected failures must return 1

 * Bindings:
  - glib-2.0: Add to_string() for GLib.PollFd and GLib.Pid
  - gtk+-3.0: Update to 3.24.13+3822ac74

Vala 0.40.18
============
 * Various improvements and bug fixes:
  - codegen:
    + Use G_TYPE_INSTANCE_GET_INTERFACE to get vtable for base-access
    + Fix setting of generic-type properties for gobject chain up [#654702]
    + Make type-parameter properties readable [#190]
    + Fix vfunc signature of delegate-typed property in interface
    + Fix support of dynamic DBus methods
  - vala:
    + Warn when passing arrays to typeof(), except for "string[]" [#868]
    + Don't falsely resolve binary-expression to bool [#869]
    + Do not allow += for arrays with fixed length
    + Array with fixed length don't require explicit instantiation [#720]
    + Infer array length of inline allocated arrays for fields [#644046]
    + Do not allow to .resize() on arrays with fixed length
    + Do not allow to change .length of arrays with fixed length
    + Improve error message for arrays as type arguments
    + Improve error reporting for invalid interface prerequisites [#437]
    + Write value of constants/enums in fast-vapi if constant only [#461]
    + Don't require constant initializer in fast-vapi [#461]
    + Restore DestroysInstance behaviour for non-compact classes [#873]
    + Report error for async creation expression without yield
  - parser: `owned` is not allowed on Constants
  - girparser: Detect and replace "-" in parameter names
  - girwriter: Add readable="0"/private="1" attribute to type-specific fields
  - gidl:
    + Calculate size correctly, avoid use-after-free
    + Avoid use of uninitialized "markup" warning
    + Ignore flags like -mfpmath=sse, -msse or -msse2
  - valadoc:
    + libvaladoc: Fix parameter and property ownership declarations
    + Fix ownership declarations of Constants
  - pkg-config:
    + vala: Add missing gmodule-2.0 to Requires.private of pkg-config file
    + libvaladoc: Move gmodule-2.0 to Requires.private of pkg-config file

 * Bindings:
  - glib-2.0: Guard against passing null source to GLib.Memory.copy()
  - gtk+-3.0: Skip _MountOperationHandler* symbols
  - libusb-1.0: Don't depend on glib-2.0
  - libusb-1.0: Remove unused private "malloc" binding
  - linux: Add memfd_create(2)
  - posix: Bind some essential memory allocation functions