[libmicrohttpd] 0.9.62 doesn't build on Visual Studio

[Jonathan McDougall]

This commit[1] made a lot of changes to digestauth.c, including using
a bunch of VLAs, which are not supported in all compilers, one of which
is Visual Studio.

If you want to keep supporting Visual Studio, those will have to be
arrays of constant size, or allocated on the heap.

[1] 
https://gnunet.org/git/libmicrohttpd.git/commit/src/microhttpd/digestauth.c?id=bcba3f58c5fc9b4a3776494d3edddceb244ab110

-- 
Jonathan McDougall