MFC r276218:
patch: Bring in xstrdup and use it when appropriate.
The function savestr allows NULL return values during Plan A patching so in
case of out of memory conditions, Plan B can step in. In many cases, NULL
value is not properly handled, so use xstrdup here (it's outside Plan A/B
patching, which means that even Plan B relies on successful operations).
Clean up some whitespaces while here
Obtained from: OpenBSD
git-svn-id: svn://svn.freebsd.org/base/stable/10@276807
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