vala: upgrade 0.56.16 -> 0.56.17

vala: upgrade 0.56.16 -> 0.56.17

* Various improvements and bug fixes:
 - codegen:
   + Add missing initializers for private fields of GSourceFuncs
   + Update array length variable passed to null-terminated ref parameter
   + Properly pass through a null-terminated out argument
   + Refactor and cache parameter in loop
   + Only handle null-terminated array as such if there is no length given
 - vala:
   + Allow declaration of static nested methods (local functions)
   + Correctly use Path.build_path()
   + Point to the invalid initializer on error
   + Report invalid type in property assignment attempt
   + Inherit important attributes for Property backing field

* Bindings:
 - glib-2.0: Avoid unnecessary copying operations in FileStream.read_line()
 - glib-2.0: Add SPACING_MARK, deprecate COMBINING_MARK
 - glib-2.0: Add dev_t/gid_t/pid_t/uid_t/socklen_t types for compatibility
 - gnu: add binding for flock(2) and its constants

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