Fix for MSVC builds

Seems that MSVC doesn't define alloca, it defines _alloca which is in malloc.h

```diff
@@ -71,6 +71,11 @@
 #include <sys/ioctl.h> /* Needed for get_columns */
 #endif

+#if defined(_MSC_VER)
+#define alloca _alloca
+#include <malloc.h>
+#endif
+
 #ifdef TLF_FONTS
 #include <wchar.h>
 #include <wctype.h>
```