* process.c: use rb_w32_uchdir() instead of plain chdir() on Windows.
reported by naruse via twitter.
* process.c (rb_execarg_addopt): need to convert to ospath.
* process.c (rb_execarg_parent_start1): need to convert the encoding to
ospath's one.
* process.c (rb_execarg_addopt): need to convert the encoding to
ospath's one.
merge revision(s) 53346,53347,53348,53349,53391,53928: [Backport #11898]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@53929 b2dd03c8-39d4-4d8f-98ff-823fe69b080e