rebuild for dmd 2.018

[Max Samukha]

This is just to make rebuild usable with dmd 2.018. Tested only on
Windows. If there are problems, you'll have to fix them yourself or
wait for an official update.

http://www.d-coding.com/downloads/rebuild-dmd-2.018.zip contains a
patch for rebuild sources. It also includes a precompiled Windows
binary. The binary requires pthreadGC2.dll, which you can grab from
ftp://sourceware.org/pub/pthreads-win32/dll-latest/lib/