[gtk] (14 commits) ...Merge branch 'testsuite-asserts' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  4d1075a... testsuite: Reduce the use of g_assert (*)
  8c156e6... testsuite: Reduce the use of g_assert (*)
  9d3aa2c... gsk: Avoid compiler warnings without assertions (*)
  5e7b5fe... gtk-demo: Avoid compiler warnings without assertions (*)
  367dfee... Fix unused variable warnings (*)
  ecfba2d... Inspector: Fix a possible undefined use (*)
  6e40f4f... Remove assertions in tests (*)
  13ece4e... Make gtk_test_init work without assertions (*)
  f98353c... Force g_test_init to cooperate (*)
  31e08d4... gsk/ngl: Build with G_DISABLE_ASSERT enabled (*)
  a871a1b... build: Don't append multiple flags as a string (*)
  b0990aa... wayland: Build with G_DISABLE_ASSERT (*)
  4164abd... build: Quiet the compiler (*)
  0c3dd0c... Merge branch 'testsuite-asserts' into 'master'

(*) This commit already existed in another branch; no separate mail sent