Refine `Time#(to_s|inspect)`

For the following reasons:

- Ruby compatibility.
- Add UTC offset (time zone informations was not included by #4433).
- More readable.

Example:

  Before this patch:

    p Time.gm(2003,4,5,6,7,8,9)        #=> Sat Apr  5 06:07:08 2003
    p Time.local(2013,10,28,16,27,48)  #=> Mon Oct 28 16:27:48 2013

  After this patch:

    p Time.gm(2003,4,5,6,7,8,9)        #=> 2003-04-05 06:07:08 UTC
    p Time.local(2013,10,28,16,27,48)  #=> 2013-10-28 16:27:48 +0900

Implementation:

I use `strftime(3)` because UTC offset can be added and program size become
smaller than the other implementations (using `sprintf(3)`, self conversion
etc) in my environment.

1 files changed, 2 insertions, 2 deletions

diff --git a/mrbgems/mruby-time/test/time.rb b/mrbgems/mruby-time/test/time.rb
index c7ad35ab2..ce7b39928 100644
--- a/mrbgems/mruby-time/test/time.rb
+++ b/mrbgems/mruby-time/test/time.rb
@@ -235,11 +235,11 @@ end
 # Not ISO specified
 
 assert('Time#to_s') do
-  assert_equal("Sun Mar 13 07:06:40 2011", Time.at(1300000000.0).utc.to_s)
+  assert_equal("2003-04-05 06:07:08 UTC", Time.gm(2003,4,5,6,7,8,9).to_s)
 end
 
 assert('Time#inspect') do
-  assert_equal("Sun Mar 13 07:06:40 2011", Time.at(1300000000.0).utc.inspect)
+  assert_match("2013-10-28 16:27:48 [^U]*", Time.local(2013,10,28,16,27,48).inspect)
 end
 
 assert('day of week methods') do