string.c: fix capacity
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: fix capacity
but not number of rooms. [ruby-core:61886] [Bug #9709]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e