Make a copy of getenv("PATH") before storing for later use. Some

Make a copy of getenv("PATH") before storing for later use.  Some
getenv() implementations use the same storage for successive calls.
CGIs on OS/390 had a bad PATH due to this.  (Believe it or not, ANSI
says getenv() can do this.)

Some similar getenv() usage was left alone as it was specific to a
certain platform, and I assume that getenv() doesn't have the "issue"
on those platforms.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85427 13f79535-47bb-0310-9956-ffa450edef68