test_env.rb: fix test

* test/ruby/test_env.rb (test_win32_blocksize): fix remained size, and
  delete added envvars.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41519 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
hash.c: refine error message

* hash.c (ruby_setenv): refine error message so include the variable
  name.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41520 b2dd03c8-39d4-4d8f-98ff-823fe69b080e