Update version to `3.0.0RC`.

README.md

@@ -17,7 +17,7 @@ of the Ministry of Economy, Trade and Industry of Japan.
 
 ## How to get mruby
 
-The preview version 3.0.0 of mruby can be downloaded via the following URL: [https://github.com/mruby/mruby/archive/3.0.0-preview.zip](https://github.com/mruby/mruby/archive/3.0.0-preview.zip)
+The releace candidate version 3.0.0 of mruby can be downloaded via the following URL: [https://github.com/mruby/mruby/archive/3.0.0-rc.zip](https://github.com/mruby/mruby/archive/3.0.0-rc.zip)
 
 The stable version 2.1.2 of mruby can be downloaded via the following URL: [https://github.com/mruby/mruby/archive/2.1.2.zip](https://github.com/mruby/mruby/archive/2.1.2.zip)
 

include/mruby/version.h

@@ -57,7 +57,7 @@ MRB_BEGIN_DECL
 /*
  * Patch level string. (optional)
  */
-#define MRUBY_PATCHLEVEL_STR "preview"
+#define MRUBY_PATCHLEVEL_STR "RC"
 
 #ifndef MRUBY_PATCHLEVEL_STR
 # if MRUBY_PATCHLEVEL < 0
@@ -80,17 +80,17 @@ MRB_BEGIN_DECL
 /*
  * Release year.
  */
-#define MRUBY_RELEASE_YEAR 2020
+#define MRUBY_RELEASE_YEAR 2021
 
 /*
  * Release month.
  */
-#define MRUBY_RELEASE_MONTH 10
+#define MRUBY_RELEASE_MONTH 2
 
 /*
  * Release day.
  */
-#define MRUBY_RELEASE_DAY 16
+#define MRUBY_RELEASE_DAY 3
 
 /*
  * Release date as a string.