test_econv.rb: assert_separately

* test/ruby/test_econv.rb (test_default_external): use
  assert_separately for clearer messages.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42383 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32.c: fix wrong trimming

* win32/win32.c (wstr_to_mbstr, mbstr_to_wstr): fix wrong trimming.
  WideCharToMultiByte() and MultiByteToWideChar() do not count
  NUL-terminator in the size for conversion result, unless the input
  length is -1.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42384 b2dd03c8-39d4-4d8f-98ff-823fe69b080e