[FS#1038] Upgrade dnsmasq to 2.78 (security fixes for remote code execution)

[LEDE Bugs]

The following task has a new comment added:

FS#1038 - Upgrade dnsmasq to 2.78 (security fixes for remote code execution)
User who did this - Jim Gettys (jgettys)

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Here is RedHat's analysis.
https://access.redhat.com/security/vulnerabilities/3199382

This is much more than the usual problem: it has multiple critical problems.

Quote from RH:

"Three of these vulnerabilities (CVE-2017-14491, CVE-2017-14492, and CVE-2017-14493) have been rated as Critical, while the remaining four (CVE-2017-14494, CVE-2017-14495, CVE-2017-14496, and CVE-2017-13704) have been rated as Important. "
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1038#comment3537