compile.c (iseq_calc_param_size): hoist out of iseq_set_arguments

This will be reused for iseq loading.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48593 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-11-27

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48594 b2dd03c8-39d4-4d8f-98ff-823fe69b080e