`Enumerable#detect` {and `#find`} should call `ifnone`; fix #4484

It's an error in ISO specification; 15.3.2.2.4 and 15.3.2.2.7

mrblib/enum.rb

@@ -65,22 +65,20 @@ module Enumerable
   end
 
   ##
-  # Call the given block for each element
-  # which is yield by +each+. Return
-  # +ifnone+ if no block value was true.
-  # Otherwise return the first block value
-  # which had was true.
+  # Return the first element for which
+  # value from the block is true. If no
+  # object matches, calls +ifnone+ and
+  # returns its result. Otherwise returns
+  # +nil+.
   #
   # ISO 15.3.2.2.4
   def detect(ifnone=nil, &block)
-    ret = ifnone
     self.each{|*val|
       if block.call(*val)
-        ret = val.__svalue
-        break
+        return val.__svalue
       end
     }
-    ret
+    ifnone.call unless ifnone.nil?
   end
 
   ##

test/t/enumerable.rb

@@ -45,7 +45,7 @@ end
 
 assert('Enumerable#detect', '15.3.2.2.4') do
   assert_equal 1, [1,2,3].detect() { true }
-  assert_equal 'a', [1,2,3].detect("a") { false }
+  assert_equal 'a', [1,2,3].detect(->{"a"}) { false }
 end
 
 assert('Array#each_with_index', '15.3.2.2.5') do
@@ -64,7 +64,7 @@ end
 
 assert('Enumerable#find', '15.3.2.2.7') do
   assert_equal 1, [1,2,3].find() { true }
-  assert_equal 'a', [1,2,3].find("a") { false }
+  assert_equal 'a', [1,2,3].find(->{"a"}) { false }
 end
 
 assert('Enumerable#find_all', '15.3.2.2.8') do