Log Message:
vala: update to 0.56.3.

Vala 0.56.3
===========
 * Various improvements and bug fixes:
  - vala: Don't unconditionally expect ObjectType of Class [#1341]
  - vala: Make try-statement parsing more resilient [#1304]
  - vala: Avoid problems with '\' in #line directives on Windows [#1353]
  - gidlparser: Set source reference of parameters

 * Bindings:
  - atspi-2: Fix a few binding errors
  - glib-2.0: Use g_abort for GLib.Process.abort() beginning with 2.50 [#1350]
  - gtk+-3.0: Correctly unhide BindingSet.by_class to avoid Version attribute