ruby.c: reject NUL in $0
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60215 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
ruby.c: reject NUL in $0
char. process title is a NUL-terminated string.
[ruby-core:82425] [Bug #13829]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60215 b2dd03c8-39d4-4d8f-98ff-823fe69b080e