win32.c: fix wrong trimming
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42384 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32.c: 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