purge 6.x-1.5-rc1

A release candidate with a few bugfixes since the 1.4 release:
- Issue #1362990 by jaydub: Bug in watchdog.
- Issue #1299776 by djbobbydrake: Sending purge request via purge method should retain url query string.
- Issue #1327216 by mauritsl,msonnabaum,chx,mongolito404: Fixed Thousands of calls to curl_multi_exec
- Issue #1403072 by jaydub: Fixed bad variable passed to watchdog
Please give it a spin and report any issues you encounter.
The 1.x will not be receiving new features. The porting of features from the 7.x-2.x branch will be decided on a case by case basis.