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!!!
Merge pull request #151 from detlefreichl/dev

make stock_browser.rb sample gtk3 ready

Patch by Detlef Reichl. Thanks!!!
gstreamer: suppress a warning

    rbgst.c:110:16: warning: passing argument 1 of ‘rbgobj_make_boxed’ discards ‘const’ qualifier from pointer target type [enabled by default]
goocanvas sample: use more specific name

Fix undefined method `prepend_environment_path'

ref: commit 510a0c216688d0209ecd5c8ec33e8eeaab3a07ee
Merge pull request #152 from myokoym/use-more-specific-name

goocanvas sample: use more specific name

Patch by Masafumi Yokoyama. Thanks!!!
gi: use "value" instead of "in"

"in" is too generic. There are other input argument type such as
function argument and callback argument.
gi: use "in" instead of "call"

It should support all input argument conversion.
glib2: support unowning boxed object