webkitgtk-2.4: security update, fix and parallel build

NEWS claims security fixes:
CVE-2014-1344, CVE-2014-1384, CVE-2014-1385, CVE-2014-1386,
CVE-2014-1387, CVE-2014-1388, CVE-2014-1389, CVE-2014-1390.
Otherwise NEWS seems safe, basically only containing bugfixes.

Parallel building should work now, thanks to make update :-)
tested with 8 threads, once webkitgtk24x and webkitgtk2.