Use assert_separately to speed up on test-all

This creates large string and it pressure GC.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39932 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Suppress -Werror=shorten-64-to-32

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39933 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_syntax.rb: envutil

* test/ruby/test_syntax.rb (test_syntax): require envutil for
  assert_valid_syntax.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39934 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_syntax.rb: pass srcdir

* test/ruby/test_syntax.rb (test_syntax): need to pass the source
  directory, __FILE__ in assert_separately is '-' because the code is
  passed via a pipe.  and this test can't finish in 10 seconds.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39935 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* iseq.c (iseq_load): get rid of SEGV.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39936 b2dd03c8-39d4-4d8f-98ff-823fe69b080e