Add --elf32-nsim-props option to run-tests.sh. This option allows a convenient way to specify path to nSIM properties file. Also change name of respective environment variable to the one that starts with ARC_.

2013-06-07  Anton Kolesov <anton.kolesov@synopsys.com>

    * run-tests.sh: Add --elf32-nsim-props option to specify nSIM properties
    file.
    * dejagnu/nsim-extra.exp: Use conventional environment variable name for
    nSIM properties file path.