mostly fix rb_iseq_load

This allows reporters commenters of [Feature #8543] to load
instruction sequences directly.  Some test cases are still failing
but documented in test/-ext-/iseq_load/test_iseq_load.rb.

* compile.c (rb_iseq_build_from_exception): entry->sp is unsigned
  (iseq_build_callinfo_from_hash): account for kw_arg
  (iseq_build_from_ary_body): update for r35459
  (CHECK_STRING, CHECK_INTEGER): remove unused checks
  (int_param): new function for checking new `params' hash
  (iseq_build_kw): new function for loading rb_iseq_param_keyword
  (rb_iseq_build_from_ary): account for `misc' entry and general
   structure changes
  [Feature #8543]
* iseq.c (CHECK_HASH): new macro (for `misc' and `param' entries)
  (iseq_load): account for `misc' and `params' hashes
  (iseq_data_to_ary): add final opt to arg_opt_labels,
   fix kw support, account for unsigned entry->sp
* ext/-test-/iseq_load/iseq_load.c: new ext for test
* ext/-test-/iseq_load/extconf.rb: ditto
* test/-ext-/iseq_load/test_iseq_load.rb: new test

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48705 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* properties.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48706 b2dd03c8-39d4-4d8f-98ff-823fe69b080e