Merge branch 'maint'

Merge branch 'maint'

* maint:
  vala tests: source test-init.sh, not ./defs
  tests: fix a spurious typo-related failure
  tests: remove spurious leftover use of 'Exit'
  tests: can check our recipes avoid trailing backslashes
  vala: improve comments to AM_PROG_VALAC
  news: update w.r.t. recent vala changes
  vala: if no proper compiler found, set $(VALAC) to 'valac'
  vala: AM_PROG_VALAC should not produce an error for tool-old valac
  docs: document recent changes to AM_PROG_VALAC
  tests: enhance tests on AM_PROG_VALAC
  vala: style fixes in vala.m4
  vala: add action arguments, for when no proper vala compiler is found

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>