add Gtk::Image #set_from_icon_set #set_from_stock #set_from_gicon
gtk3: remove a needless space before "("
gtk3: indent
glib2: add rbg_check_hash_type()
glib2: use RUBY_T_HASH

We dropped Ruby 1.8.
glib2: add rbg_check_array_type()
glib2: fix wrong force conversion method

to_array ->
to_ary
glib2: add rbg_to_array()
glib2: add rbg_to_hash()
gi: support invoking with GVL unlock

CAUTION: This change breaks internal API compatibility. Libraries that
use "invoke" should be changed.
gi: remove needless RUBY_T_* check

We had dropped Ruby 1.8 support.
gst: follow ruby/gi API change
clutter: follow ruby/gi API change
clutter-gtk: follow ruby/gi API change
gi: add GVL unlock detect API to loader
gstreamer: unlock GVL for methods that may use another thread

[ruby-gnome2-devel-ja]

Reported by NAKAJIMA Takashi. Thanks!!!
make stock_browser.rb sample gtk3 ready
gstreamer: sample stepping (nearly working)