merge revision(s) r42988: [Backport #8928]

	* parse.y (intern_str): sigil only names are junk, at least one
	  identifier character is needed.  [ruby-dev:47723] [Bug #8928]

	* parse.y (rb_enc_symname_type): fix out of bound access.


git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/branches/ruby_2_0_0@44845 b2dd03c8-39d4-4d8f-98ff-823fe69b080e