Update version to 4.0.0RC.

README.md

@@ -51,6 +51,8 @@ To get mruby, you can download the stable version 4.0.0 from the official mruby
 GitHub repository or clone the trunk of the mruby source tree with the "git
 clone" command. You can also install and compile mruby using [ruby-install](https://github.com/postmodern/ruby-install), [ruby-build](https://github.com/rbenv/ruby-build), [rvm](https://github.com/rvm/rvm), [conda](https://anaconda.org/channels/conda-forge/packages/mruby/overview) or [Homebrew](https://formulae.brew.sh/formula/mruby).
 
+The release candidate version 4.0.0 of mruby can be downloaded via the following URL: [https://github.com/mruby/mruby/archive/4.0.0-rc.zip](https://github.com/mruby/mruby/archive/4.0.0-rc.zip)
+
 The latest development version of mruby can be downloaded via the following URL: [https://github.com/mruby/mruby/zipball/master](https://github.com/mruby/mruby/zipball/master)
 
 The trunk of the mruby source tree can be checked out with the

include/mruby/version.h

@@ -57,7 +57,7 @@ MRB_BEGIN_DECL
 /*
  * Patch level string. (optional)
  */
-#define MRUBY_PATCHLEVEL_STR ""
+#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 2025
+#define MRUBY_RELEASE_YEAR 2026
 
 /*
  * Release month.
  */
-#define MRUBY_RELEASE_MONTH 4
+#define MRUBY_RELEASE_MONTH 3
 
 /*
  * Release day.
  */
-#define MRUBY_RELEASE_DAY 20
+#define MRUBY_RELEASE_DAY 5
 
 /*
  * Release date as a string.