Add pluggable versioning by mruby-version
Fix release date
replace Kernel.show_version with MRUBY_DESCRIPTION
Add global constant MRUBY_COPYRIGHT
Fix MRUBY_BIRTH_YEAR
introduce mrb_str_new_lit() to create strings from C string litrals
use mrb_str_new_lit() more widely
remove unnecessary semicolon
Merge pull request #1688 from cubicdaiya/issues/unnecessary_semicolon

Remove unnecessary semicolon
Merge branch 'master' into iij