gc.c: unit suffix

* gc.c (get_envparam_size): accept unit suffix 'k', 'm', and 'g'.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44936 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-02-14

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44937 b2dd03c8-39d4-4d8f-98ff-823fe69b080e