Update to 38.8.0

Changelog:
Fixed in Firefox ESR 38.8
    2016-47 Write to invalid HashMap entry through JavaScript.watch()
    2016-44 Buffer overflow in libstagefright with CENC offsets
    2016-39 Miscellaneous memory safety hazards (rv:46.0 / rv:45.1 / rv:38.8)
    2016-36 Use-after-free during processing of DER encoded keys in NSS
    2016-29 Same-origin policy violation using performance.getEntries and history navigation with session restore
    2016-15 Use-after-free in NSS during SSL connections in low memory
    2016-07 Errors in mp_div and mp_exptmod cryptographic functions in NSS

(ryoon)