make build options.c with VS2008 compiler

Cannot build options.c in pygit2 v0.20.3 with Visual Studio 2008 compiler. Patch makes build options.c with the compiler.
```
c:\Program Files\Microsoft Visual Studio 9.0\VC\BIN\cl.exe /c /nologo /Ox /MD /W3 /GS- /DNDEBUG "-IC:\Program Files\libgit2\include" -Iinclude -IC:\python\include -IC:\python\PC /Tcsrc\options.c /Fobuild\temp.win32-2.6\Release\src\options.obj
options.c
src\options.c(47) : error C2143: syntax error : missing ';' before 'type'
...
```