Bug 858231: Update NSS to NSS 3.15 Beta 6, with the local patch
revert-bug-808217.patch. r=wtc.
Reduces revert-bug-808217.patch to just avoid using the new
SECITEM_ReallocItemV2 function.
Inclues fixes for bug 868694, bug 868678, bug 873673, bug 783579,
bug 808217.