Fixed #317: invalid range check in Char#each_byte

spec/std/char_spec.cr

@@ -112,4 +112,10 @@ describe "Char" do
     ('a' <=> 'a').should eq(0)
     ('b' <=> 'a').should be > 0
   end
+
+  it "raises on codepoint bigger than 0x10ffff when doing each_byte" do
+    expect_raises do
+      (0x10ffff + 1).chr.each_byte { |b| }
+    end
+  end
 end

src/char.cr

@@ -156,7 +156,7 @@ struct Char
       yield (0xe0 | c >> 12).to_u8
       yield (0x80 | c >> 6 & 0x3f).to_u8
       yield (0x80 | c & 0x3f).to_u8
-    elsif c <= 0x1fffff
+    elsif c <= 0x10ffff
       # 11110xxx  10xxxxxx  10xxxxxx  10xxxxxx
       yield (0xf0 | c >> 18).to_u8
       yield (0x80 | c >> 12 & 0x3f).to_u8