Security update for webkit2gtk3 (important)

This update for webkit2gtk3 fixes the following issues: Update to version 2.18.5: + Disable SharedArrayBuffers from Web API. + Reduce the precision of "high" resolution time to 1ms. + bsc1075419 - Security fixes: includes improvements to mitigate the effects of Spectre and Meltdown CVE-2017-5753...