* develop:
  Remove reference to internal Heap functions for now
  Some cleanup of testing code
  Add call to AppVeyor env setup
  Do we need spaces?
  Try again...
  Change vcvars syntax
  Check visual studio env var
  Correct vcvarsall location
  Add Visual Studio 2013 build as well as 2015
  Reinstate .travis.yml
  Update cd command
  Use HTTPS git checkout instead of SSH
  Another Python3 try
  Update Python3 version
  Try AppVeyor build with local broker
  修改了restoreCommand时：（1）topics指针未申请内存的问题；（2）unsub误写为sub的问题。
  fix issue that MQTTClient_connect hangs on network outage, for windows

# Conflicts:
#	src/Socket.c
#	test/test6.c
Signed-off-by: Juergen Kosel <juergen.kosel@softing.com>