Phobos pull 613

[Brad Anderson]

This pull [1] adds std.net.curl to the Windows makefiles (it has 
been missing for the last couple of releases). It'd be great if 
this could be merged before the next release. Denis figured out 
what was preventing the autotester from working (this is what 
prevented my pulls to fix this from getting applied) so it should 
be good to go now.

I had a pull for the Windows installer which has already been 
applied which automatically downloads the curl binaries. That 
change, combined with Denis' pull, should make curl support for 
Windows as simple as it can be (as long as you use the installer) 
while meeting Walter's desire to not bundle curl binaries with 
phobos.

Could a phobos committer please review this pull and merge it 
before 2.060 is released?  Then we won't get the recurring 
question of why std.net.curl isn't working on Windows.

[1] https://github.com/D-Programming-Language/phobos/pull/613

Regards,
Brad Anderson