On Windows, Bad Things happen when apr_proc_create() is allowed to pass TRUE
to CreateProcess(bInheritHandles). For instance, the open handle for a new
installer executable file being downloaded by the background updater gets
inadvertently passed to a couple slplugin.exe instances. When the viewer
finishes downloading, closes the file and tries to remove it, Windows balks
because the file is still open by another process. Require an apr_suite
package that includes the new Linden apr_procattr_inherit_set() extension, and
call it to turn off CreateProcess(bInheritHandles).