Make default rule more permissive in YANG lexer (rouge-ruby#1488)

Although strings of the form `+abc*iu` should be tokenised as correct
by the Yang lexer, they currently produce errors. This commit fixes
this problem by reducing the characters excluded by the default rule.

lib/rouge/lexers/yang.rb

@@ -140,7 +140,7 @@ def self.types
           end
         end
 
-        rule %r/[^;{}\s*+'"]+/, Name
+        rule %r/[^;{}\s'"]+/, Name
       end
     end
   end

spec/lexers/yang_spec.rb

@@ -68,6 +68,16 @@
           ['Punctuation', ';']
       end
 
+      it 'parse complex name' do
+        assert_tokens_equal ' +abc*iu{ asd;}',
+          ['Text.Whitespace', ' '],
+          ['Name', '+abc*iu'],
+          ['Punctuation', '{'],
+          ['Text.Whitespace', ' '],
+          ['Name', 'asd'],
+          ['Punctuation', ';}']
+      end
+
     end
 
   end