Appveyor Windows 64-bit builds fail because the compiler is broken
Since about 6 hours ago, all Appveyor 64-bit Windows builds fail the first C file they build with:
```
bash.exe : In file included from ../src/core/or/or.h:16,
At line:2 char:5
+ & $commandPath $args 2>&1
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (In file include...ore/or/or.h:16,:String) [], RemoteException
+ FullyQualifiedErrorId : NativeCommandError
from ../src/app/main/ntmain.c:22:
../src/lib/cc/torint.h:52:2: error: #error "Seems that your platform doesn't use 2's complement arithmetic. Argh."
#error "Seems that your platform doesn't use 2's complement arithmetic. Argh."
^~~~~
In file included from ../src/core/or/or.h:26,
from ../src/app/main/ntmain.c:22:
../src/lib/cc/compat_compiler.h:28:2: error: #error "It seems your platform does not represent NULL as zero. We can't cope."
#error "It seems your platform does not represent NULL as zero. We can't cope."
^~~~~
../src/lib/cc/compat_compiler.h:32:2: error: #error "It seems your platform does not represent 0.0 as zeros. We can't cope."
#error "It seems your platform does not represent 0.0 as zeros. We can't cope."
^~~~~
In file included from ../src/core/or/or.h:16,
from ../src/feature/dirauth/dircollate.h:16,
from ../src/feature/dirauth/dircollate.c:25:
../src/lib/cc/torint.h:52:2: error: #error "Seems that your platform doesn't use 2's complement arithmetic. Argh."
#error "Seems that your platform doesn't use 2's complement arithmetic. Argh."
^~~~~
In file included from ../src/core/or/or.h:26,
from ../src/feature/dirauth/dircollate.h:16,
from ../src/feature/dirauth/dircollate.c:25:
../src/lib/cc/compat_compiler.h:28:2: error: #error "It seems your platform does not represent NULL as zero. We can't cope."
#error "It seems your platform does not represent NULL as zero. We can't cope."
^~~~~
../src/lib/cc/compat_compiler.h:32:2: error: #error "It seems your platform does not represent 0.0 as zeros. We can't cope."
#error "It seems your platform does not represent 0.0 as zeros. We can't cope."
^~~~~
```
https://ci.appveyor.com/project/teor2345/tor/build/1.0.113/job/ujbvwntcu1pdk2m6#L762
CC'ing mikeperry, because he's on CI rotation this week.
Which is weird, because configure seems to succeed.
issue