rb_iseq_location_t: change first_lineno type to VALUE

Nearly all current uses of iseq->location.first_lineno are as a
VALUE, not a size_t.  The only exception was the experimental
(and currently unused) rb_iseq_build_for_ruby2cext function.

* vm_core.h (rb_iseq_location_t): change first_lineno type to VALUE
* iseq.c (rb_iseq_build_for_ruby2cext): update based on argument

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47269 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-08-25

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47270 b2dd03c8-39d4-4d8f-98ff-823fe69b080e