Add Windows testing with AppVeyor

[ararslan]

This runs on my AppVeyor account to avoid using up the JuliaLang paid AV queue.

Closes #165.

[ararslan]

Windows 32-bit is working, but 64-bit says

set PATH=C:\MinGW\bin;%PATH%
mingw32-make.exe ARCH=%ARCH%
gcc   -fno-gnu89-inline -fno-builtin -O3 -fPIC -m64 -std=c99 -Wall -IC:/projects/openlibm -IC:/projects/openlibm/include -IC:/projects/openlibm/amd64 -IC:/projects/openlibm/src -DASSEMBLER -D__BSD_VISIBLE -Wno-implicit-function-declaration -IC:/projects/openlibm/ld80 -c src/common.c -o src/common.c.o
src/common.c:1:0: warning: -fPIC ignored for target (all code is position independent)
 #include <openlibm_math.h>
 ^
src/common.c:1:0: sorry, unimplemented: 64-bit mode not compiled in
Make.inc:145: recipe for target 'src/common.c.o' failed
mingw32-make.exe: *** [src/common.c.o] Error 1
Command exited with code 2

[ararslan]

Okay, I'm stumped.

[nalimilan]

mingw32-make.exe ARCH=%ARCH%

Should it be mingw64-make on 64-bit?

[ararslan]

Currently it's working on 64-bit and not on 32-bit, so I don't think make is the problem.

[ararslan]

Interesting, the problem on 32-bit now is that it can't find mingw32-make...

[ViralBShah]

Any thoughts what needs to be done here?

[ararslan]

I haven't looked at this in quite a while. I still have no idea why it isn't working and I don't have access to a Windows machine or VM to test locally.

[ViralBShah]

Maybe disabling the 32-bit stuff so that the 64-bit stuff works would be still better. Right now appveyor just gives a red everywhere until we merge something here.