merge revision(s) 43449,43514,43525: [Backport #8879] [Backport #8883]

	* load.c (ruby_init_ext): share feature names between frame name and
	  provided features.

	* load.c (rb_feature_p): deal with default loadable suffixes.

	* load.c (load_lock): initialize statically linked extensions.

	* load.c (search_required, rb_require_safe): deal with statically
	  linked extensions.

	* load.c (ruby_init_ext): defer initalization of statically linked
	  extensions until required actually.  [Bug #8883]

	* load.c (ruby_init_ext): defer initialization of statically linked


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@43656 b2dd03c8-39d4-4d8f-98ff-823fe69b080e